There could be no better introduction to an article on the Panama Canal than the enthusiastic words of Ambassador Bryce in a recent chapter on the Isthmus of Panama, where he says, in referring to the canal:
There is something in the magnitude and the methods of this enterprise which a poet might take as his theme. Never before on our planet have so much labour, so much scientific knowledge, and so much executive skill been concentrated on a work designed to bring the nations nearer to one another and serve the interests of all mankind.
In no previous age could an enterprise so vast as this have been carried through; that is to say, it would have required a time so long and an expenditure so prodigious that no rational government would have attempted it.
It is true we have elsewhere done work of comparable magnitude—the tunnels under the Hudson and East Rivers, the great railroads and terminals, the Erie Canal, the city subways and water-supply systems, the reclamation projects and great bridges—but these are all intimately interwoven with our daily life and progress. The canal is a project crystallized from the vast multitude of enterprises and is indisputably the greatest of them all.
With a subject so vast, and one that has attained historic interest and ranks as an engineering work of such magnitude, it seems necessary to give a resume of the early history, and consider it in connection with events that may be well known in other connections.
EARLY HISTORY.
One of the most interesting subjects connected with the Panama Canal is the history of the canal idea. To study its conception carries us back to the Middle Ages—to the conditions so well described by Fiske in his "Discovery of America," when Genoa and Venice were the great commercial rivals and Spain was a rising power. Following Marco Polo's marvelous travels from 1269 to 1295, throughout Asia, and that of his adventurous successors, a great trade developed with the Orient, which proceeded unchecked via the Mediterranean and the ancient overland routes until the hostile Mohammedan Turk, recovering from two centuries of repression from the Crusades, overflowed his own dominions and entered the Balkan peninsula. In 1453 Constantinople was taken by the Turks, and the alliance between that city and Genoa was broken. This great commercial metropolis, through the persistent attacks of the Turks, was gradually deprived of her route to the Orient and thus of her commerce. The commerce of Genoa's great and only rival, Venice, had a similar fate.
Tremendous pressure developed for the finding of some new route to Cathay, as the other conditions for trade were most favorable. The world's ideas of geography at that time were of the crudest fashion. America was unknown. Africa had not been circumnavigated; its southern limits were enveloped in a haze of conjecture and ignorance. It was known that Asia did not extend indefinitely to the East and was not bounded by limitless swamps, as had been supposed. With the increasing hazards of the route to Cathay and the lands of spices, and the rising expectations of wealth and riches fed by the avaricious and adventurous spirit of the Middle Ages, the minds of men were forced to think of the possibility of other routes.
In the discovery by Dias, in 1486, and the confirmation by Vasco de Gama, in 1496, of the route to India by circumnavigating Africa, we are not now interested except to know that the Presence on the first of these voyages of the brother of Christopher Columbus acted as a stimulus to the mind of the great explorer. He, as we know, put the unique idea of reaching Cathay by sailing westward to the test of four actual sea voyages. The results we know, but we must bear in mind that the discovery of the American continent was a mere incident and that What Columbus was really seeking was a passage to the Orient, and for this he continued his search on his three subsequent voyages. His ships ran their noses into the bays and inlets in the hope that they might forge on to the desired lands. The full truth was never known to Columbus; he little realized, when his ships were at Porto Bello, that only forty miles overland were the waters—could he only reach them—which would carry him to his much-sought-for goal, and thence to Spain. Succeeding explorers continued these efforts, and every indentation of the eastern coast line of the Americas was explored by Spanish, Portuguese, English and Dutch ships, only to dim the hopes that the passage could ever be found.
It remained for Balboa, led on by tales of friendly Indians, to gain the knowledge of what lay beyond, after an overland journey not far distant from the site of the present canal. The discovery of the Pacific in 1513 only intensified the mariners' desires to Penetrate with their ships.
The discovery in 1520, by Magellan, of the straits named after him, his entry into the Pacific, and the completion of the circumnavigation of the globe in 1522 by a part of his expedition, did not solve the problem and only emphasized the desirability of a conveniently located passage.
The actual results of the epoch-making discoveries overshadowed the original aims of the explorers. From being a primary aim, the search for the interoceanic passage, with the gradual ushering into the known world of the two continents, became secondary. The exploration and development of the newly found lands afforded a boundless outlet for the restless Spirit of the times. The canal idea, having had its genesis in such great world events, was now to enter the next stage of its development.
It is remarkable that the desire for the passage has persisted throughout all these centuries. The increase in geographic knowledge, the correct understanding of the relation of the Americas to Europe and Asia, political history, the invention and building of railroads, and finally, the phenomenal development of the American continent itself, have all brought out new phases of the problem and altered the point of view; but in all its phases it has remained one of the great ambitions of the human race.
The Americans will not have the honor of sending the first ship across the Isthmus. Balboa and his successor, Gil Gonzales de Avila, both carried ships across—Balboa after building them near the source of lumber supply on the Atlantic side and then dismantling and re-erecting them on the Pacific side, and de Avila after dismantling the ships that had carried him across the ocean. Their enterprise and energy are greatly to be admired. Untold difficulties beset the journeys through the jungle, and in Balboa's first crossing, one authority states the number of deaths amongst the Indian cargadores to have been five hundred, and another places the number at two thousand. The object in crossing the Isthmus was exploration on the Pacific side, especially investigations of the reputed gold in Peru. Subsequently there was much traffic with the Pacific coast, which was carried across the Isthmus and reshipped.
Charles V of Spain, who succeeded to the throne in 1516, encouraged the explorations of the South Sea, as the Pacific .was then known, and urged his American governors, if possible, to discover a strait by systematic exploration. The expedition of Gil Gonzales de Avila along the Pacific shores had this object. He discovered Lake Nicaragua, which has played such an important part in the interoceanic canal question. No strait being found after years of search, Charles in 1534, by a royal decree directed examination to be made of the land between the Atlantic town of Chagres and the Pacific with a view to the establishment of water connection. It is reported that even as early as 1520 surveys were ordered by the Emperor. The result of the royal decree was that the local governor declared the work to be impracticable and beyond the resources of any sovereign.
In the meantime a considerable commerce developed across the Isthmus. The city of Panama was founded on the Pacific side in 1517, and Nombre de Dios, founded in 1519, was the most important post on the Atlantic side. Between the two a road was built and a series of posts established. Later Porto Bello, due to a better harbor and superior location, was made the Atlantic terminus and 'a new road to Panama was built of such a character that portions of it may be used to this day. Subsequent to 1534 a partial water route was established for boats and light-draft vessels up the Chagres as far as Cruces by removal of obstructions from the river. This is the identical stream and valley which nearly four hundred years later is being utilized as the Atlantic end of the Isthmian Canal. The establishment of the partial water route did not lead to the discontinuance of the paved way. With the conquest of Peru by Pizarro in 1533-1535, the trans-isthmian trade grew in amount and value and the Spanish colonies continued to prosper. Panama became a great collecting and distributing center for Spanish commerce.
So lucrative and so extensive did the trade become that under Philip II, who succeeded to the throne on the abdication of Charles V in 1555, the search for a strait was given up and all idea of a canal abandoned. With untold treasures coming to Spain by the existing means of transport, the Emperor did not desire to seek new means of intercourse which might benefit a rival nation as much or more than Spain, and furthermore all the energies of the people were fully occupied in developing the existing sources of treasure and none seemed available for new enterprises. The same policy continued for about two centuries.
In the meantime trade developed and the terminal towns grew. Panama in its day was the great metropolis of the New World having pretentious stone churches, monasteries and numerous dwellings of wood. Its markets and those of Porto Bello were the meeting-places for the merchants of Peru, the Isthmus, and of Spain. Great quantities of silver and gold passed eastward and supplies from Spain came in the opposite direction. The transportation across the Isthmus was by mule train. All others than Spanish were excluded from the traffic; the richness of the trade and the overbearing stand of the Spaniards encouraged piratical attacks by the seamen of the northern nations on the shipping of the Atlantic and Pacific coasts, and even on the overland mule trains. Between the years 1570 and 1596 Sir Francis Drake made numerous privateering attacks which were very much of the nature of piracy. The Spaniards were sending their merchant ships in fleets twice a year, convoyed by six and eight armed vessels. Drake was followed in his enterprise by the buccaneers who reached the limit of their power under Henry Morgan. Morgan with great energy and daring ,captured Nombre de Dios and immediately after conducted operations against Porto Bello. He turned what was nearly a failure into a cruel success, and a year later, in 1671, according to his threatened promise to the governor of Panama, he returned to ransack the city of Panama. After a wretched trip across the Isthmus, almost without food, the city was attacked and fell into the hands of Morgan. As a result of his raid the city was destroyed, and to this day the ruins of old Panama, the massive stone walls and towers of churches, monasteries and forts still remain as mute and impressive evidences of the constructive energy of the Spaniards and of the wicked, destructive energy of the English buccaneers. After a systematic plunder of all the valuables of the city, Morgan left. The town was never rebuilt in the old location.
The trade of Panama suffered a period of decline after the Indian empires had been stripped of their valuables. A royal cedula in 1593, forbade trade with China and the East Indies; the development of local industries was forbidden through rival influences at home; corrupt governors did the colonies no good, and there were various governmental restrictions on trade and growth. Even the roadway across the Isthmus entered a period of disuse, and the traffic between Spain and the Western ports went via the Cape of Good Hope or Cape Horn, except a certain amount crossing at Tehuantepec.
In the latter part of the eighteenth century certain desultory efforts were made toward a canal, including an examination of the Nicaragua route in 1779 to 1781, followed by a discouraging report. Even so, a company was formed to undertake the project and selected a route utilizing Lake Nicaragua. By 1823, when all the continental colonies had secured their independence by revolt, all Spanish effort and influence ceased.
MODERN CANAL PROJECTS.
With the demise of Spanish authority on the continent there was an early active revival of canal projects. In fact, as early as 1825 the minister of the then Central American Republic to the United States addressed the Secretary of State, inviting attention to the willingness of the Republic to receive the cooperation of the United States in the building of a canal by a group of American merchants. The United States gave a favorable reply, but nothing resulted then. In 1826, however, the Republic of Central America actually accepted the proposals of an association for the building of the canal under liberal terms. The attempt to organize a company with $5,000,000 of capital proved unsuccessful. In 1830 the Central American Republic negotiated with a Netherlands company, and the United States hearing of this, informed the Republic that it would expect the same rights and privileges of passage through the canal as other nations. In 1835, at the initiative of the United States some investigations were begun, but were dropped in 1837 upon the advice that the time was not propitious. Another project started in 1838, and a still further Investigation and an estimate of $25,000,000 were made in President Van Buren's administration, but the Isthmian country was too unsettled and revolutionary for any definite progress to be made. There are records of still other efforts in 1826, 1827 and 1838. In the latter year a concession was granted to a French company to build roads or canals. As a result a canal was recommended by Napoleon Garella with a starting-point in Limon Bay, thence to a connection with the Chagres River below Gatun. The divide was to be crossed by means of a series of eighteen locks on the Atlantic side and sixteen on the Pacific side, with a summit level 158 feet above the sea, and the highest part of the divide penetrated by a tunnel over three miles long. The report of actual conditions by Garella discouraged the promoters.
During all this period the United States was peopled only on the Atlantic seaboard and was interested in commerce which started or terminated in Atlantic ports only. In the middle of the century events occurred which were destined to greatly increase the importance of the Isthmus, and to have a strong influence in pushing the canal idea to the point where its actual execution was bound to follow. It was the acquisition of California, the discovery of gold therein, the exploration and settlement of the Northwest Territory, and to a lesser extent the purchase of Alaska, which led the United States on to its destiny as a Pacific as well as an Atlantic power and thus established the conditions that ultimately made the canal a certainty. The trans-isthmian route for freight and passengers regained its old-time importance, and curiously enough it was again the search for gold that gave the impetus. A railroad across the Isthmus followed promoted by Americans. The success of this road was continuous on account of the increasing amount of traffic. Even the establishment of the transcontinental railroads did not vitiate the importance of the trans-isthmian road, nor did any of the railroads have a real deterrent influence on the canal scheme.
Almost innumerable projects, examinations and reports were made during the latter half of the nineteenth century, in which the United States, France and Great Britain led. Prior to 1850 no extensive and accurate surveys had been made. After that date work was done in earnest; no longer were the results of reconnoissances afoot or on horseback sufficient; the methods of modern engineering were taking their first grip upon large enterprises, and no company or government could entertain a proposition not based on surveys by .engineers and on detailed estimates of cost. Several companies were incorporated, including the American, Atlantic and Pacific Ship Canal Company in 1850. All failed from one reason or another to do much more than organize or conduct surveys. Always some insuperable obstacle was met. It is no doubt true that very few fully realized the enormous difficulties that subsequent experience disclosed, and fortunately so, since the enthusiasm for the idea might have received a setback from which it could not have easily recovered. A predicted cost of $400,000,000 would have made the enterprise seem impossible.
In 1869 official recognition was given to the subject, and President Grant's first message to Congress called attention to the advisability of an American canal on American soil. The appointment of a commission was authorized by Congress, known as the Inter-Oceanic Canal Commission, who not only examined all available data previously gathered by others, but had new data collected and had access to new surveys made principally under the direction of officers of the army and navy, covering the Panama, Nicaragua and Darien routes. In 1876, after six years work, the commission reported that "After a long, careful, and minute study of the several surveys of the various routes, the one known as the Nicaragua route . . . . possesses, both for the construction and maintenance of a canal, greater advantages and offers fewer difficulties from engineering, commercial, and economic points of view than any of the other routes."
A further survey of the Nicaragua route was made in 1885 by order of the Secretary of the Navy. This was followed in two years by the organization of the Maritime Canal Company of Nicaragua, incorporated by Congress and having a concession from the Nicaraguan government. The company actually dug a portion of the canal on the Atlantic side, but failing to secure government aid the concession lapsed and the property reverted to the State.
In 1895 the Nicaragua Canal Board was appointed by the President by authority of Congress. The board visited Nicaragua, conducting investigations, but in the six months allowed them did not have sufficient time for further necessary explorations, for collecting the vast amount of information and reaching a definite conclusion on so momentous a matter, and accordingly recommended a further board. As a result the Nicaragua Canal Commission of 1897 was appointed, and in its report of May 1899, proposed a route which followed closely the one suggested in 1852. The United States was apparently committed to the Nicaragua route. The Panama route had been pre-empted by the French, but their hold was loosening. Congress in its next step authorized a further commission with greatly extended authority, to consider the Panama as well as the Nicaragua route and to evaluate work done by any private company, having in mind the French. The first Isthmian Canal Commission was accordingly appointed in 1899—a distinct broadening in scope and title from, those of the previous boards and commissions.
FRENCH CONTRIBUTION TO THE ENTERPRISE.
At this point it is well to pause in the account of American doings, to consider briefly what the French had contributed since the middle of the century to the canal idea and to construction. In 1844 a French engineer, after surveys having both a railway and a canal in view, made an accurate report concerning Panama, all in the interests of a French company holding concessions. Like so many others the project failed and the concessions lapsed. At the Congress of Geographical Science in 1875, in Paris, M. Ferdinand de Lesseps came upon the scene with the sweeping announcement that in his opinion the authors of all plans up to that time had committed the serious error of examining only canal routes with locks, and that the interoceanic canal in order to meet the requirements of navigation, must be constructed at sea-level like the Suez. Thus early did he show that the elements of his character—force, unbridled enthusiasm, convictions without investigation, and a sublime faith in himself—which had carried him on to a magnificent success in the straightforward problem at Suez, were, in the infinitely more difficult problems at Panama, to make of him a consummate blunderer and a deceiver, brushing aside and ignoring the advice and estimates of competent and trained engineers when they did not follow his own preconceived ideas, and leading many unfortunate investors, including himself, to financial ruin. Under such a leader the French project was foredoomed to failure. De Lesseps, so far as the French were concerned, made the project his own; he dominated the committees, moulded a popular sentiment, all being eager to follow his lead; if doubts arose, his was the reassuring word, and at his solicitation the subscriptions to the stock of the company poured in. His success at Suez was his most valuable asset and had indeed placed him on a pinnacle. He was a man of undoubted ability, but lacked an element of discrimination which should have caused him to appreciate the true magnitude of the problems before him. De Lesseps having attempted great projects must be measured by great standards. He did not lack strong opposition nor able expert advice, but he beat them down with the same indiscriminating ability as he did natural obstacles and the financial troubles that interfered with his idealized delusion of a sea-level canal.
In 1876, a French committee with De Lesseps at the head was formed; also, in 1876, a civil association undertook actual surveys, which were under the direction of Lieut. L. N. B. Wyse. In May, 1878, after completing the surveys, Lieutenant Wyse secured for his association a concession from the government of Colombia for a ship canal. This was the real beginning of the canal which, after many vicissitudes, is now almost completed. An international congress of surveys was held in Paris in 1879, and after elaborate discussion decided on the route from the Bay of Limon to the Bay of Panama, and that it should be at sea level. The decision for the sea-level canal was by no means unanimous. "When one reads the reports of the sessions of that commission, one constantly recognizes the inspiration of M. de Lesseps, one perceives the action of his will, so persistent in forming a general opinion in favor of a plan for a canal on a level." There were those who foresaw the difficulties and who advocated a lock canal. In fact, de Lesseps had against him the majority of the engineers and contractors. The predicted cost was 1,200,000,000 francs, and the time twelve years. About three months later the Universal Interoceanic Canal Company was formed, but less than one-tenth the stock was subscribed on the first attempt. De Lesseps did not have a bed of roses; he consented to new surveys and new estimates, and he personally went to the Isthmus in December, 1879, accompanied by the International Survey Commission. The surveys were accomplished and the conclusions reached in a time so incredibly short as to cast doubt upon their reliability. The estimate of cost was 834,000,000 francs, and of time eight years, both remarkably lower than those of the year before by the technical commission. The estimate of cost was still further reduced to 685,000,000 francs by de Lesseps himself, leaving it less than sixty per cent of the original estimate, which was considered low by competent persons. Later a firm of contractors, Couvreux & Hersent, favorable to the views of de Lesseps, estimated the cost of the canal to be 500,000,000 francs, and they undertook a contract on a cost-plus-profit basis. The annual revenue of the completed canal was estimated at 90,000,000 francs. The stock issue of 300,000,000 francs was doubly subscribed. The contractors performed the two years of preparatory work at cost plus six per cent. By the end of that time, December, 1882, it was clear that the predicted unit costs and rates of progress could not be reached, and the contract was annulled on the contractors' proposal.
The Superior Advisory Commission was formed in 1881, composed of men eminent as engineers and technicians. This commission was dominated by de Lesseps through his personal force, and their acts did not result in clearing the situation.
To carry on the work abandoned by the closing of the contract, the canal company in 1883 secured the services of M. Dingler, an able engineer, to supervise and direct the operations on the Isthmus. The developments of the next few years were a voluminous report by the chief engineer on the sea-level canal project; discovery that the quantity to be excavated was 120,000,000 cubic meters, rather than the 75,000,000 estimated by the International Commission or the 45,000,000 estimated by the International Congress; the award of a series of small contracts and establishment of work yards; the realization in July, 1885, that less than one-tenth of the excavation had been completed although four of the eight years allowed for construction had elapsed; the return to the former estimate of 1,200,000,000 francs; a reorganization involving the award of large contracts for completing the canal in five sections by 1889; the announcement by de Lesseps, in 1886, after a visit to Panama of his utmost confidence in the speedy completion of the canal; further successful bond issues; renewed attacks on the feasibility of the sea-level canal based on reports by expert engineers of incontrovertible facts, but ineffective on de Lesseps; the weakening of public and financial support, and the final capitulation of de Lesseps to the lock-canal idea, but only as a temporary expedient to hasten completion and to be followed by a deepening to sea level. These events were followed by the ineffectual attempt to issue a series of lottery bonds on authority of the Chamber of Deputies, which foreshadowed the financial debacle of the enterprise. Receivers were soon appointed and the affairs of the company were wound up. De Lesseps and his son were tried, convicted and sentenced by the courts of France to pay a fine and serve a term of five years imprisonment. The sentence against the son was reversed, and that against the father was never executed. He became a complete wreck, both physical and mental, and died in 1893. The company had actually expended about 1,300,000,000 francs and had accomplished about 55,000,000 cubic yards of excavation on the permanent work, or less than one-half the total on the French plan.
After careful investigation and a great deal of difficult work, the receiver, in 1894, launched a new company to complete the lock canal. An extension of time had been secured from the Colombian government through the agency of Lieutenant Wyse. The first step of the new company was to reinvestigate the whole subject of the canal, which was done through the appointment of the "Comite Technique" of engineers of international eminence, including two Americans. Their work was most thorough, comprehensive, and to the point. Later, in accordance with the charter of the company, a commission of five members was appointed to make final recommendations, who reported:
. . . that the adopted project is practicable under the conditions of time and expense indicated, and that the New Company has demonstrated that by works which will not exceed an outlay of about one hundred million dollars, and a duration of about ten years, it is possible to open the Panama Canal to extensive commerce, to remove the obstacle which the Isthmus Opposes to international communication, and thus to complete an immense work that interests all the nations of the world and is the greatest which human genius has ever planned.
There was to be a summit level and an artificial lake at Bohio with the necessary locks, 738 feet long and 82 feet wide, and sea-level connections. There is every reason to believe that the enterprise was feasible and would have been carried through. The company, as a matter of fact, did only enough work to care for the extensive plant and excavated about 5,000,000 cubic yards in five years, but the valuable and necessary progress made was in the way of gathering scientific information that was absolutely essential and which the old company did not have, and which later proved of the greatest benefit to the United States. The financing of the enterprise became impracticable, due to the .United States coming into the field as a probable canal builder. The French were truly leading a forlorn hope and finally their only chance lay in selling out to the United States.
TRANSFER OF CONTROL TO THE UNITED STATES.
The Isthmian Canal Commission of the United States, in the two and one-half years from June, 1899, to November, 1901, made most elaborate investigations of the whole canal problem, covering the first Darien route from the Gulf of San Blas to the Gulf of Panama; the second Darien route from Caledonia Bay to San Miguel Bay, an arm of the Gulf of Panama; the Panama route from Limon Bay to Panama Bay; and the Nicaragua route from Greytown via the San Juan River and Lake Nicaragua to Brito on the Pacific, and other less important routes. An immense amount of literature, reports and surveys turned out by Previous boards was accessible, including the most excellent and Complete data in the hands of the New French Company. Besides all this, much additional surveying and investigation was a necessity.
The commission evaluated the French property as follows:
Useful Canal Excavation $21,020,386.00
Chagres Diversion 178,186.00
Gatun Diversion 1,396456.00
Railroad Diversion 300,000.00
Contingencies 4,579,005.00
Panama Railroad Stock6,850,000,00
Maps, Drawings and Records 2,000,000.00
Total $36,324,033.00
Add about 10 per cent to cover omissions 3,675,967.00
Grand total $40,000,000.00
The French company submitted an estimated valuation for purpose of discussion with a view to sale to the United States, of $109,141,500.00. The commission estimated the cost of completing the Panama Canal to be $144,233,358.00, to which must be added the commission's evaluation of the French property, or a total of $184,233,358.00, or adding the company's offer to the cost of completion, a total of $253,374,858.00. The commission estimated the cost of building the Nicaragua Canal to be $189,864,062.00.
A lock type was found to be obligatory on the Nicaragua route, and either a sea-level or lock canal was found possible on the Panama route, but the commission strongly recommended the lock canal and reported on the relative advantages of the two schemes as follows:
The estimated annual cost of maintaining and operating the Nicaragua Canal is $1,300,000.00 greater than the corresponding charges for the Panama Canal.
The Panama route would be 134.57 miles shorter from sea to sea than the Nicaragua route. It would have less summit elevation, fewer locks, 1568 degrees and 26.44 miles less curvature. The estimated time for a deep draft vessel to pass through is about 12 hours for Panama and 33 hours for Nicaragua. These periods are practically the measure of the relative advantages of the two canals as waterways connecting the two oceans, but not entirely, because the risks to vessels and the dangers of delay are greater in a canal than in the open sea.
Except for the items of risks and delays, the time required to pass through the canals need to be taken into account only as an element in the time required by vessels to make their voyages between terminal ports. Compared on this basis, the Nicaragua route is the more advantageous for all trans-isthmian commerce except that originating or ending on the west coast of South America. For the commerce in which the United States is most interested, that between our Pacific ports and Atlantic ports, European and American, the Nicaragua route is shorter by about one day. The same advantage exists between our Atlantic ports and the Orient. For our Gulf ports the advantage of the Nicaragua route is nearly two days. For commerce between North Atlantic ports and the west coast of South America the Panama route is shorter by about two days. Between Gulf Ports and the west coast of South America the saving is about one day.
The commission's recommendation was that,
After considering all the facts developed by the investigations made by the commission and the actual situation as it now stands, and having in view the terms offered by the New Panama Canal Company, this Commission is of the opinion that "the most practicable and feasible route" for an Isthmian Canal, to be "under the control, management, and ownership of the United States," is that known as the Nicaragua-route. When this information reached Paris the French company were at our mercy and capitulated with a cabled offer to sell for $40,000,000.00, to the United States. The Isthmian Commission then made a supplementary report, dated January 18, 1902, as follows:
The unreasonable sum asked for the property and rights of the New Panama Canal Company when the Commission reached its former conclusion overbalanced that route, and now that the estimates by the two routes have been nearly equalized the Commission can form its judgment by weighing the advantages of each and determining which is the more practicable and feasible . . . After considering the changed conditions that now exist, the Commission is of opinion that "the most practicable and feasible route" for an Isthmian Canal, to be "under the control, management, and ownership of the United States" is that known as the Panama route.
The report and plans of the commission of 1899-1901 are most comprehensive covering the subject from the earliest times, and forming a veritable mine of information.
The American desire for a trans-isthmian canal had now become a determination. The demands of commerce were intensified, and the trip of the U. S. S. Oregon around South America had made clear the immense potential value of the canal to the navy. During the succeeding moves the American side of the case was handled with great skill and acumen, for which the able report of the Isthmian Commission had paved the way.
The Spooner law became effective on June 28, 1902, and authorized:
(a) The purchase of the rights and property of the New Panama Canal Company at $40,000,000.00, including the stock of the Panama Railroad.
(b) Acquiring from the Republic of Colombia perpetual control of a strip of land, together with all water rights, and the right to build and perpetually maintain a canal, together with the right to exercise sanitary control over the strip of land and the cities at either end.
(c) The actual building of the canal on the Panama route.
(d) The making of all arrangements for the complete building of a canal on the Nicaragua route, should the negotiations with Colombia or with the New Panama Canal Company prove unsuccessful.
(e) The creation of an Isthmian Canal Commission of seven members, four of whom were to be skilled engineers, and of the four, one to be an officer of the Engineer Corps of the United States Army, and one an officer of the United States Navy.
(f) The act appropriated $10,000,000.00, to be immediately available and authorized a further sum of $135,000,000.00 (besides the $40,000,000.00 for purchase of the canal company's property) in case of adoption of the Panama route, or of $185,000,000.00 in case of adoption of the Nicaragua route.
During the negotiations with Colombia the hopes of the stockholders in the French company were alternately raised and dashed as the trend of affairs indicated the adoption of the Panama or of the Nicaragua route. The Colombian government which had the sovereign rights over the Isthmus, failed to ratify the treaty, and soon thereafter the Department of Panama led a successful revolt. The new Panama government, after being recognized by the United States, concluded a treaty which was very satisfactory and which was proclaimed February 26, 1904. The purchase from the French Canal Company was soon consummated, and on May 4, 1904, the United States took possession of the site and property. The occasion was a momentous one. The men who had accomplished so much in clearing the way for the building of the canal, looked forward with confidence to its speedy and successful construction. There were many others who looked with fear and trepidation upon the undertaking. There was a general feeling that after almost four centuries of reports, investigations, surveys and failures, it was time for the dirt to fly immediately. Fortunately those placed in charge of the work were trained in the scientific planning of large undertakings, and while certain excavation work was done to appease the popular demand, and also to secure experimental data for excavating and planning, the great problems of the moment were recognized as three in number: first, to decide on the type, form and exact location of the canal; second, to outline the method of attack and to purchase and assemble the vast amount of equipment and material; third, to perfect an organization of the administrative and working forces.
PHYSICAL CHARACTERISTICS OF THE CANAL ROUTE.
While the size and character of the canal were open questions, the general location was determined. The line of cut adopted by the French had been selected by some of the early exploiters; the Panama Railroad had been located in the same valleys and depressions; and the French had actually begun to build along this line. At this point it is well to consider briefly the character and topography of the canal route and adjacent territory as it was before any work was done, but bearing the future canal in mind. The Isthmus of Panama if it joined the two continents by the shortest line would extend northwest toward North America and southeast toward South America; but it does not follow the shortest line, and on the map looks as if South America had been pushed northwestward and the narrow part of the Isthmus on the end toward South America had been bent out of shape with a bulge to the north and the concave side to the south, almost forming a semicircle enclosing the Gulf of Panama. (See plan No. 1) Near the head of this Gulf is an indentation known as the Bay of Panama. This bay touches that part of the rough semicircle where the Isthmus sweeps to the northeast toward the top of the semicircle, and where a line at right angles to the Isthmus is about northwest. This northwest line from the Bay of Panama ends in the Bay of Limon, on the Atlantic side, and happens to pass through the region where the Continental Divide is much lower than anywhere else and where the Isthmus is less than 36 miles wide, only 5 miles wider than at the very narrowest point. The line if slightly distorted may be made to pass for three-fourths of its length along the valley of the Rio Grande River on the Pacific side, and the Valley of the lower Chagres on the Atlantic side, except that the Chagres before reaching Limon Bay turns off to the left to its mouth, seven miles west of the bay, while the line continues straight to Limon Bay. This is in general terms the course of the canal.
The Bay of Limon faces almost directly north, and has an opening three miles wide into the Caribbean Sea, and extends five miles inland of the full width. The depth of the water varies form 5 feet to 36 feet. (See plan No. 2.) The Atlantic end of the French canal was cut through the swamps along the east shore of Limon Bay and extended into the bay, so as to make use of Colon as a protection from northerly seas. Limon Bay, on the Westerly and inland sides, is surrounded by much higher land, except that the lowlands of the small Midi River valley extend inland from the above-named swamps almost through the ridge, which is here very low. The narrow strip of lowland continues inland beyond the Midi River valley and dips into the Chagres valley near Gatun. One would almost have expected the Chagres River to seek outlet straight ahead in Limon Bay, only three miles distant; but the little ridge between the Chagres and the headwaters of the Midi River prevented this, and so the Chagres follows the lowlands behind the ridges surrounding Limon Bay and discharges into the Carribean Sea about seven miles west of the bay. At Gatun, where the line of the canal first meets the Chagres, the valley is about a mile and a half wide, but as we follow upstream it becomes very much wider. The stream is sluggish and winds in and out amongst the swamp lands.
Just above Gatun the Chagres receives an important tributary, the Gatun River. It was of some importance in the plans for any canal of which the sea-level portion extended inland beyond Gatun, for either the canal had to cross the river, to take its flow, or otherwise the river must be turned off before reaching the canal by a new channel or diversion to the sea. The French actually built a very wide diversion to the. sea, 8 miles long. The Trinidad River enters the Chagres from the other side, about three miles above Gatun.
Throughout this portion of the Chagres the water-surface is but little above the sea-level, and it so continues as far as Bohio, 16 miles inland by the canal line from Colon. At Bohio the valley contracts, and this was the site selected for the locks and dams in the French canal, and in one of the early American plans. The land surface from Bohio upstream becomes gradually more undulating and the slopes of the valleys become steeper. At Bas Obispo, 13 miles inland from Bohio by canal line, or 29 miles from Colon, the low water level of the river rises to 45 feet above the sea. Up to this point the Chagres valley leads in a fairly direct line toward the Pacific Ocean, and fortunately approaches the low point of the Continental Divide. Now the canal line must leave the Chagres, for the river makes an abrupt turn and to follow it to its sources would carry us into the mountains to the northeast; that is, into the apex of the roughly semicircular part of the Isthmus. The canal builder cannot dismiss the river from his mind at the point where the line of the canal leaves the valley, for some of the most important problems of the canal are dependent upon the character of the stream above Obispo, and to these we shall return.
At Bas Obispo the Chagres River is joined by its tributary, the Obispo River, the valley of which offers the best opportunity for continuing the canal for the next 4 miles. The continental ridge begins at Bas Obispo, and with it the hills become higher. The stream is tortuous, and the canal line cannot follow it but must be cut on more direct lines to avoid objectionable curvature.
The elevation of the ground is constantly increasing, reaching a low summit at Empire, and the highest summit at Culebra, where the future canal passes between Gold Hill and Contractors Hill. The highest elevation of the ground on the center line is 312 feet above sea-level, but the highest part of the sloping sides will be 554 feet above sea-level. Culebra is about 6 miles from Obispo, and about 35 miles from Colon. The country falls much more rapidly on the Pacific side, and 3 miles beyond Culebra, close to Pedro Miguel, the level is lower than at Obispo, 8 miles back.
The Continental Divide covers a distance of 9 miles from Bas Obispo through Empire and Culebra to Pedro Miguel, and of this the deepest part is 6 miles in length from Las Cascades to a point near Pedro Miguel, and forms the heaviest part of the socalled Culebra Cut. From Pedro Miguel to Miraflores, a distance of 1 ½ miles, the land continues to fall, and the canal fortunately finds the low valley of the Rio Grande as an available path to the Pacific. This valley from Miraflores to the sea is very little above the sea-level, while beyond the lowlands it is lined on both sides with much higher ground and hills, of which Sosa Hill and Ancon Hill are the best-known. The distance from Colon to Miraflores is about 393/2 miles, and from Miraflores to the Pacific is 5 ½ miles, or a total of about 45 miles from Colon to the shores of the Pacific.
The waters of Panama Bay vary in depth from 7 to 32 feet, and the bottom slopes off into the deeper waters of the Gulf of Panama and the Pacific Ocean. (See plan No. 3.) About 23/2 miles off shore from the mouth of the Rio Grande is a group of islands with both low-lands and mounds. The question as to whether the canal should pass to the east or to the west of them was decided one way by the French and the opposite way by the Americans, the reasons for which will develop later.
Having thus observed the principal natural features of the canal route, we may note to what extent the topography was affected by the French operations, paying but little attention to the period from 1889 to 1904, for the New Panama Canal Company did only enough to hold the charter.
As already noted, the French canal was excavated from Colon through the lowlands on the easterly shore of Limon Bay, and as far as Gatun it was later used by the Americans for carrying materials to the locks. It was partly excavated as far as Bohio, a total distance of about 17 miles.
The bottom width of the canal was not over 72 feet, and the depth of water averaged about 20 feet for half the length, and over the part toward Bohio where the ground was higher, did not go below sea-level. The canal crossed the Chagres River at several points, and the river water flowed freely into the canal. At Gatun, where the canal leaves the river bed, about one-third of the flow continued through the canal. The large bend in the river is "short-circuited" by a cut-off known as the Chagres diversion. There were also a number of other such diversions. At Bohio considerable rock excavation was done after the sea-level canal was given up in favor of a lock canal. From Bohio to Bas Obispo the canal excavation cut the course of the Chagres a great many times. Across the Continental Divide the French cut a comparatively narrow trench, which at its deepest point was 165 feet below the original surface, and left about 190 feet more of cut to accomplish a sea-level canal, and over 100 feet for the French lock canal. On the Pacific end a partial channel was dredged, and also the necessary diversions on each side which captured the water from the river branches and discharged it into the bay before it could reach the canal. A total amount of 80,000,000 cubic yards of excavation was done all along the canal. Some of it was deposited on the line of the much wider canal finally adopted by the Americans, and required reexcavating; some of the channels were partially filled by silting. Besides excavation, the French left behind them some 2000 buildings and a vast amount of equipment. Much of it was overgrown with a dense jungle during the 15 years of inactivity, and was lost until years after.
THE CHOICE OF TYPE.
With this brief excursion across the Isthmus, observing the various natural and artificial features of importance, and which an examination of the maps will aid in fixing in the mind, we are in a better position to consider the problems that confronted the United States when it was necessary to decide on the type of canal. The choice lay between a sea-level and a lock canal. The United States was determined to have the best canal regardless of cost or trouble. The French ideal was a sea-level canal which they epitomized as the "Straits of Panama." But their financial resources would not allow them to attain their ideal, so they adopted a lock canal as a makeshift and temporary expedient. Knowing this, the American tendency was to regard the sea-level canal as something more difficult to attain and, therefore, as something more valuable and more desirable. Furthermore, the average citizen or average official is unfamiliar with locks, and these devices convey to him an idea of something vague and hazardous. These feelings had first to be overcome before the nation was ready to consider the question on its true merits. In view of this, of the vital necessity to the success of the enterprise of deciding the question of the type of canal correctly, the President appointed an International Board of Consulting Engineers to advise in the decision as to type and probable cost. The board was presided over by a retired major-general of the United States Army, and included in the membership seven American and five foreign engineers, all most eminent in their profession and experienced in the problems involved in the construction of the canal.
The divided report of the board was unexpected and in a way, disappointing. Five of the American engineers favored the lock type, but they were in the minority, as the chairman, the two remaining American engineers, and all the five foreign engineers voted for the sea-level canal. Five members of the Isthmian Canal Commission and the chief engineer approved and recommended the lock canal, while the other member favored the sea-level type. On a poll of individuals of both bodies, nine were for the sea-level, and eleven for the lock canal. It remained for the Secretary of War and the President to consider, with the various reports of facts and statements of relative advantages and disadvantages before them, which type was to be adopted.
Not only was the sea-level canal of inferior dimensions and greater cost, but its winding channel was not conducive to good navigation, and the time which a vessel in the high-level canal would lose in the locks would be lost in the sea-level canal in slowing down for passing other vessels on account of the very narrow channels; in fact two vessels of any size could not pass in the 21 miles of 150-foot width unless one of them tied up in Specially provided turnouts. The sea-level canal was not considered superior from the standpoint of safety; the sinking of a single ship could block the canal indefinitely; the many stream diversions along the banks of the canal and the great dam at Gamboa were potential sources of danger in time of flood to a canal which was in the lowest part of the valley.
It is illuminating to read the following extract from the comment of Secretary of War Taft, on the report of the Board of Consulting Engineers:
When I visited the Isthmus a year and a half ago and went over the site and talked with the then chief engineer, I received a strong impression that the work of construction upon which the United States was about to enter was of such world-wide importance and so likely to continue in active use for centuries to come, that it was wise for the government not to be impatient of the time to be taken or of the treasure to be spent. It seemed to me that the sea-level canal was necessarily so much more certain to satisfy the demands of the world's commerce than a lock canal that both time and money might well be sacrificed to achieve the best form, and this feeling was emphasized by reading the very able report of the majority. But the report of the minority, in showing the actual result of the use of the locks in ship canals, in pointing out the dangers of so narrow and contracted a canal prism as that which the majority proposes, and in making clear the great additional cost in time and money of a sea-level canal, has led me to a different conclusion.
We may well concede that if we -could have a sea-level canal with a prism from 300 to 400 feet wide, with the curves that must now exist reduced, it would be preferable to the plan of the minority, but the time and the cost of constructing such a canal are in effect prohibitory.
I ought not to close without inviting attention to the satisfactory character of the discussion of the two types of canal by the greatest canal engineers of the world, which insures to you and to the Congress an opportunity to consider all the arguments, pro and con, in reaching a proper conclusion.
The following is the essential part of the decision by President Roosevelt, dated February 19, 1906, which with the reports of the board he transmitted to Congress:
It must be borne in mind, as the Commission points out, that there is no question of building what has been picturesquely termed "the Straits of Panama" ; that is, a waterway through which the largest vessels could go with safety at uninterrupted high speed. Both the sea-level canal and the proposed lock canal would be too narrow and shallow to be called With any truthfulness a strait, or to have any of the properties of a wide, deep water strip. Both of them would be canals, pure and simple. Each type has certain disadvantages and certain advantages. But, in my judgment, the disadvantages are fewer and the advantages very much greater in the case of a lock canal substantially as proposed in the papers forwarded herewith. . . .
The law now on our statute books seems to contemplate a lock canal. In my judgment a lock canal, as herein recommended, is advisable.
On June 27, 1906, Congress passed a joint resolution which approved the lock canal proposed by the minority, and finally closed the case. This was more than one year after the appointment of the Board of Consulting Engineers. Many details as well as many problems of importance were not finally determined by the board and required consideration by the Isthmian Canal Commission. It will not be necessary to describe the detailed processes and the steps by means of which these matters were finally determined, except incidentally when studying some of the important elements of the canal. A general account of the canal as it is actually being built will now be given, to be followed by descriptions of its important parts.
GENERAL DESCRIPTION OF THE CANAL.
The sea-level approach channel from the Caribbean Sea lies within Limon Bay for 42 miles. (See plan No. 2.) It is 500 feet wide on the bottom, with side slopes of one vertical to three horizontal, and having a depth of 4 1/2 feet below mean sea-level. (See plans Nos. 4 and 5.) The range of the tide is about 2 feet. The alignment is straight for 5 1/2 miles from the entrance as far as the Mindi Hills, at which point the American canal intersects the comparatively insignificant old French canal. There is a slight bend of long radius at Midi Hills, and then a straight run of 1 1/2 miles to Gatun Locks. We have passed from the valley of the Midi River into the valley of the Chagres, and are face to face with one of the great problems of the canal construction, namely, the handling of the torrential Chagres River. After weighing several other schemes, that finally adopted consists of the formation of a lake measuring about 24 miles on the canal axis from Gatun to Bas Obispo. The length of the lake in the other direction will be over 30 miles. The lake is formed by the construction of an earth dam of unusual dimensions extending across the valley at Gatun. The dam does not seem artificial to the eye, but appears as one of the major features of the landscape. After the lake is filled, the flow of the Chagres into it will be discharged by the carefully designed concrete spillway, which cuts through the middle of the great earth dam at a point where a rocky eminence afforded a safe location. The normal water-surface of Gatun Lake will be 85 feet above mean sea-level, but provisions are made so that the water-surface can be carried at any elevation between 8o feet and 87 feet.
Ships will be passed into Gatun Lake by means of a series of three locks at Gatun, each of which in turn will raise the vessel an average of 28 1/3 feet. The locks are close together and the ships will pass directly from one lock into the next. The three locks are in duplicate; that is, a vessel may go up either one flight or the other of the duplicate locks, or one flight may be used for ascending vessels and the other for descending vessels. The corresponding locks adjoin and there is only a dividing wall between them. After the ship has passed into the lower lock, and while it is being raised, the following ship, if close behind, may be tied up at the approach wall 1200 feet long, formed by an extension of the dividing wall. Each lock has a net or usable length of 1000 feet, and a net or usable width of 110 feet, but the dimensions of the ship must be somewhat less than this to provide for clearances.
The formation of the lake with the water 85 feet above the sea-level obviated all digging for 17 miles, except the top of an occasional mound. (See plan No. 5.) The alignment of the channel in the lake was determined by the position of hills, changed into islands by the rising water.
At the locks, the canal axis makes d slight bend to the left and the channel of moo feet width and 75 feet depth extends in a straight line for 3 1/2 miles to the first bend in the lake. This bend is followed by a straight channel of the same width but reduced depth for a distance of 4 2 miles, almost to Bohio, where a further turn to the left is made. The course does not run straight to Bohio from the locks, because Tiger Hill and Lion Hill are in the way. After a two-mile run from Bohio to Buena Vista, moo feet wide, there is a turn to the right, the course continuing straight for a distance of 272 miles to a point opposite Frijoles. Here there is a further turn to the right, with a straight course of 2 ½ miles, still moo feet wide, to a point near Tabernilla; then a turn to the left, with a reduction in width to 800 feet, and a straight reach of 3 miles to a point near San Pablo. The lake has now become a narrow arm, occupying the region where the valley of the Chagres had much steeper banks. At San Pablo there is a turn to the left with a short run 800 feet wide of one mile; then a turn to the right, another short run of 1 mile, with a further turn to the right; then a longer reach of 3 miles, with width reduced to 500 feet, passing the submerged town of Gorgona; then a right turn and a t-mile run to a point near Gamboa. From Gatun to Gamboa there are 23 crossings of the former course of the Chagres, showing that the canal has practically followed the course of the river, but with the aid of steam shovels has selected a much straighter course than the one carved by the river along the lines of least resistance.
At Bas Obispo, which is close to Gamboa, we enter the great Culebra Cut. The minimum width of the canal up to this point has been 5oo feet, but through the following 8.1 miles the bottom width is reduced to 300 feet to save excavation. The banks of the canal become higher and higher as we pass on, until at Gold Hill, the elevation of the highest land on one side is 554 feet above sea-level, and the other side, 410 feet, while the land over the center of the canal was formerly 312 feet above sea-level, or 227 feet above the bottom of the canal. The minimum depth of the canal on the entire upper level is 45 feet at normal lake-level, or 40 feet at low lake-level, but throughout Gatun Lake the depth is in excess of these. The Culebra Cut and the 85-foot elevation of the water both end at the Pedro Miguel Lock. In passing through the cut, from Bas Obispo to Pedro Miguel, there are eight straight reaches connected by easy curves, three to the right and four to the left. It is most remarkable that so large a portion of this run is on straight lines, and that the total degree of curvature has been kept so low.
At Pedro Miguel there is one lock in duplicate which lowers the vessel to the 55-foot elevation of Miraflores Lake. The Pedro Miguel Lock has approach walls formed by 1200-foot extensions in both directions of the dividing-wall between the locks. Miraflores Lake is comparatively small, and a run of 12 miles, in a 500-foot channel 45 feet deep, takes the ship to Miraflores. At this point there are two locks in duplicate, with approach walls at the upper and lower levels, the same as at Pedro Miguel and Gatun. The two locks at Miraflores lower the vessel to tide-water, a drop of 45 feet at high tide, or 65 feet at low tide. (See plan No. 3.) The 20-foot tides on the Pacific coast have made the problem more difficult than on the Atlantic coast, where the tide is only 2 feet. One-half mile beyond Miraflares Locks the canal makes a turn to the right and extends for a distance of 2 1/2 miles to Balboa, where it makes a turn to the left and extends for 4 1/2 miles to deep water in the Bay of Panama. The Pacific sea-level section is all of 5oo feet width, and the depth of the water is 55 feet at high tide and 35 feet at low tide, and is usually stated to be 45 feet deep, referring to mean tide.
The total length of the canal, measured along its axis, is 50.4 miles. The portion within the shore lines is only 41.5 miles, and the remainder consists of dredged channels in Limon Bay and Panama Bay. Of the total length, 14 1/2 miles are at sea-level, over 23 1/2 miles in Gatun Lake, nearly 3 miles in the locks or alongside approach walls, 1 1/2 miles in Miraflores Lake and 8 miles in the Culebra Cut. In the total length there are 22 bends, with a total curvature of 600 degrees and 51 minutes. The average length of the straight reach is a little over 2 miles. At each bend the canal is widened by cutting away on the inside of the bend, the shape and amount of cutting having been determined after observations of vessels actually rounding turns.
The time required for a vessel to pass through is estimated to be from 10 to 12 hours, of which 3 hours is required for passing the locks. Through the Culebra Cut the vessel must reduce Speed, but for most of the remaining distance may approach full Speed.
GATUN LAKE.
Less attention, it is believed, has been paid to Gatun Lake by those describing the canal than the subject really deserves.. (See Plan No. 1.) It forms the preponderant element in the American project. The great dam at Gatun, the spillway, and the locks are only incidental to the lake, and by virtue of it the amount of excavation and the attendant difficulties in the Culebra Cut are greatly reduced.
The lake provides 2332 miles of canal channel, or nearly half the total length, and gives a width of moo feet for 16 miles, 800 feet for 4 miles, and 500 feet for the remaining 4 miles; the average width is nearly 900 feet, while the rest of the canal averages less than 450 feet. Not only in width, but also in depth the lake channel offers an advantage, for while the rest of the channel is limited to an ample depth of 45 feet, the lake offers a maximum depth of about 75 feet, and is nowhere less than 45 feet along the navigable channel. These generous dimensions will facilitate navigation and will allow vessels to approach their ocean speed.
Besides being such a valuable asset to navigation, Gatun Lake solves one of the most difficult and most vital of all the problems involved in the canal construction. We are familiar with the characteristics of the Chagres River. This wild and variable stream is immediately tamed and calmed on entering Gatun Lake. Its waters, which form and replenish the lake, may be likened to a beast of burden quietly carrying the ships to and fro, supplying the lifting force that passes them through the locks, and the power to drive the generators which light the canal, operate the machinery, and may later operate the railroad.
While great ideas and great accomplishments may be briefly abstracted in picturesque terms, the knowledge so given is superficial if unaccompanied by a more intimate consideration of the principles involved, and of the studies and investigations which attended them. Nothing may be left to surmise or conjecture, no assumptions may be made, unsupported by masses of the best evidence available. Where the problems are new and no direct evidence can be obtained, the best engineering judgment, based on experience, must be brought into play.
An investigation had first to be made as to the sufficiency of the water-supply. The lake, once it is formed, will suffer losses from at least five different sources: 1st, evaporation; 2d, seepage, or groundflow; 3d, leakage through the lock gates and spillway gates; 4th, water required to pass ships through the locks; and 5th, water to develop power, if a sufficient amount remains available.
Evaporation depends on the wind and the hygrometric state of the air, and also on the area of the lake. At the normal elevation of 85 feet above sea-level, the area of the lake is 163 square miles. For certain reasons that will be discussed later the elevation of the lake may, when actually placed in service, vary from 8o to 90 feet above sea-level, and the area of the lake will vary correspondingly from 153 to 173 square miles. Evaporation continues from day to day, and unfortunately is the greatest when rainfall is the least. The length of the dry season is therefore Of importance. To provide for the driest future year, the weather records as far back as available are studied, and the driest year taken as a standard, with an allowance for even more unfavorable conditions. Fortunately, the French under the New Company made continuous and careful observations of all meteorological and hydrological features of value. The Americans have continued these observations with great care and completeness. Evaporation pans have also been exposed to secure direct evidence which would bear some relation to the rate of evaporation from the lake. From the best evidence available, the probable rate of evaporation is found to be about one-fourth of an inch per 24 hours. This has been computed to equal a loss of 930 cubic feet per second.
The loss by seepage is dependent on the character of the soil forming the bottom of the lake, and of the head or pressure of water at any particular point. To clearly understand its character we may note that an ordinary river in reality includes more than the flowing water which is visible between its banks, in that the ground along the river contains water which to the eye seems quiescent, but which actually has a flow, extremely slow, but always moving toward the river and down the valley with the river. Its rate of flow depends on the character of the material, the frictional resistance, and the distance to be traveled; it is comparatively rapid in sand or gravel, and is reduced to a minimum in clays and rocks. The seepage from Gatun Lake will be Of an allied nature, and it remains to estimate the amount. The engineers made careful studies of the bottom of the lake by borings, test pits, and geological surveys. Specially careful examinations were made at those points where the ridges between the lake and the adjoining valleys are narrow and low. It was perfectly possible that gravel strata or porous coral deposits might exist which, communicating with the sea, might discharge the waters of the lake as through a sieve. The engineers satisfied themselves that no such condition existed, and their judgment was confirmed by a Board of Consulting Engineers appointed in 1908 by President Roosevelt. The probable ieepage was estimated to be 85 cubic feet per second, or less than one-tenth the rate of evaporation during the dry season.
The loss of water through leaks and imperfect seatings in the many valves and miter-gates of the locks, and the 14. gates of the spillway, depends on the accuracy with which the devices are made, and the care used in the maintenance. The commission followed correct principles in using the utmost care in designing and constructing them, and yet assuming a rather heavy loss of water from incomplete closure or accident. The amount lost is estimated to be 275 cubic feet per second, the equivalent of wo city fire streams.
The amount of water found necessary for developing electric current for lighting the canal, and operating all the machinery, is estimated at 275 cubic feet per second, based on the required amount of current and the efficiency of the apparatus.
The amount of water required for lockages is dependent on the design of the locks, the amount of traffic, and the size of the vessels, for the locks are so divided that small vessels may use short sections, or several small vessels pass through the whole lock together. Assuming the traffic equal to the maximum capacity of the locks, and utilizing records of experience with the Sault Ste. Marie Canal, the Board of Consulting Engineers estimated the traffic at 80,000,000 register tons per year, as against 30,000,000 tons for the "Soo" Canal, and an actual maximum of 15,500,000 tons for the Suez. The amount of water required for lockage was found by the designing engineers to be 2618 cubic feet per second, which means about one lockage in each direction per hour, but the assumed maximum traffic will not be reached for many years.
Adding the total losses from all causes gives a total of 4183 cubic feet per second, applicable during the dry months, when evaporation is the greatest. The question now arises: Where is this rather enormous quantity of water coming from? The input into Gatun Lake comes from rainfall directly on the lake, which is absent in the dry season, however, and from the flow of Chagres River and of minor streams. The data desired for this purpose pertains to the driest period that may be reasonably expected, and the best way to predict it is from records of the flow of the Chagres in past years. The records of the New French Panama Canal Company furnish much reliable information, while that obtained from the old company is fragmentary and incomplete.
The driest consecutive four months in the available records of 19 years show a flow on an average of 1190 cubic feet per second into the lake. Unfortunately, a 19-year period is hardly sufficient to determine the future probable minimum, and the average of 1190 cubic feet which occurred in 1908, the year the computations were made, was followed in 1912 by an average flow for four months of less than 9o0 cubic feet per second, or about 25 per cent less. This will not affect the problem adversely, because of the liberal allowances made in determining losses and the possibility of using the Miraflores oil-fired steam plant in place of Water-power.
It is apparent that the 1190 cubic feet per second supplied. To Gatun Lake will not provide the 4183 cubic feet per second to be consumed. The balance, or 2993 cubic feet per second, will be Obtained by filling Gatun Lake to a level of 87 feet above the sea (the gates and copings are 92 feet) before the end of the rainy season, and then during the succeeding dry season, drawing the lake down gradually to a level of 8o feet above sea-level, if need be. The storage capacity of the lake between these two levels, at an average area of about 159 square miles, will supply this amount of water with a slight margin. The problem is identical in many respects with that involved in the great impounding reservoirs of modern city water-works, such as those of Boston and New York, where storage tides over the dry season.
It may be noted that this drawing off of the upper 5 feet of the lake explains one reason why the depth of channel through the Culebra Cut was made 45 feet at normal lake level. The water level in the cut is the same as in the lake, and when the lake falls to 8o feet, the channel in the cut will have 40 feet depth of water.
At this point it becomes clear that one of the greatest responsibilities of the canal operating force will be the conservation of the water. The operator must be thoroughly versed in problems of rainfall and hydrology, and should begin the dry season with a full lake, and he must be careful not to be caught by an unexpectedly early or unusually dry season; he must each year be prepared for the worst. No apprehension need be felt that the water-supply will give out, however, if reasonable care is taken. Should more water be required to meet new conditions of the distant future, it may be obtained by building a reservoir on the upper Chagres, with a dam at Alhajuela, where some of the floodwaters of the Chagres may be stored until needed in the dry season. It was here that the French proposed building a reservoir for supplying the highest level of their canal through a tunnel.
We have seen that Gatun Lake can be kept full, but have yet to determine that it can be filled initially. An examination of the records of flow of the Chagres for all available years leaves no doubt that the water in the rainy season in excess of all losses is more than sufficient to fill the lake in two successive years. The driest rainy season of record, 1911-1912, afforded an average flow of 6556 cubic feet per second, which would have filled Gatun Lake in about 400 days, or two rainy seasons, making deductions for reduced losses on account of there being no lockages, no hydraulic power plant in operation, and less evaporation, leaks and seepage, due to reduced lake area and head of water.
THE GATUN DAM.
The Gatun Dam, which made Gatun Lake possible, is the key to the American Panama Canal scheme. (See plan No. 2,) The lock-level canal might have been built with a dam at a different location, such as that proposed by the French at Bohio, but the area of the lake would have been very much less, with a consequent loss of opportunity to navigate in wide, unrestricted channels, and a great loss in storage capacity. The dam at Bohio could have been built of masonry on a rock foundation, for which the French made considerable excavation. A masonry dam on rock foundation was not possible at Gatun, because the rock is too far below the surface. It was only after advice had been obtained of some of the ablest engineering talent in the world, familiar with similar problems elsewhere, that an earth dam at Gatun was decided on. This decision was probably the most momentous one in connection with the canal construction. Elaborate investigations were made of the character of the underlying material through test pits and innumerable borings. It was found that the top layer consisted of fine sand intermixed with a large proportion of clay, which extended to a maximum depth at one point of practically 8o feet. Below this, for a distance of mo feet or more, is a thick deposit of impervious blue clay, containing a little sand with a quantity of shells interspersed. Below the clay, and directly overlying the bed rock, is a miscellaneous layer of variable thickness up to 20 feet, consisting of boulders and gravel consolidated with finely divided clays and silts.
Several important factors enter into the design of this dam and the determination of its dimensions. The dam itself must be impervious to water, or on finer analysis it would be more accurate to say the seepage must be a minimum. If a well, extending below the ordinary level of the ground water, and without tapping subterranean water channels, is pumped, the ground water in the surrounding territory will flow towards the well and its level will gradually fall and assume a curve joining the surface of the water in the well with the normal ground-water level some distance away. The slope of this curve depends upon the character of the material and the amount of friction which it exerts against the flow. Deeper pumping will lower the curve and extend it farther back. To maintain a fixed level of water in the well will require a fixed rate of pumping, equal to the seepage through the ground, so long as no rain falls on the area affected by the well. The conditions at the Gatun Dam are similar, with the ground-water level in the valley below the dam corresponding to the water in the well and the water in the lake corresponding to the normal ground-water level, and the slope curve passing through the dam.
To prevent loss of water, the materials of which the dam is built must be selected from the available local deposits and placed in such a way as to retard to the greatest possible extent the flow of water. In very fine silts the rate of flow is so minute that they are generally classed as impervious. Capillary attraction is a force which must be considered. It is this which keeps the surface of ordinary ground moist. The evaporation from the surface removes the moisture, but it is promptly replaced by capillary attraction from the ground-water reservoir below. With no rain the ground water is thus gradually lowered until the capillary forces are no longer sufficient to raise the water to the surface, which then becomes dry. This force must also be considered, although to a minor extent, in the design of the dam.
Unfortunately, the ordinary materials which are classed as impervious have a faculty for absorbing water, which softens them and reduces their capacity for self-support. With the height of water furnished by Gatun Lake there is ample opportunity for the contents of the dam to become saturated, and materials subject to disintegration, or with a tendency to absorb, would not maintain the side slopes. Clay or fine silt is particularly treacherous in its nature; yet it is upon these materials that the imperviousness of Gatun Dam must depend. The solution of this problem is to build the center of the dam of impervious material and the outer portion on both sides of a material capable of maintaining the predetermined slopes wet or dry, but necessarily allowing water to Pass. On the lake side it must be faced with a lining to resist wave action.
Yet this is not all. The weight of the dam might produce so great a pressure on the original surface of the earth that it would sink and cause the earth to rise just beyond the toe of the dam. This actually happened only a short distance away with embankments for the Panama Railroad. The remedy was to counterweight the rising area of soft material at the toe of the embankment with fill material and thus prevent any further rise. With a structure like the Gatun Dam, settlement of this character would have dislodged the parts of the dam already built, would have created possible fissures and avenues for future flow, and would have aroused the greatest doubt in the minds of the public as to its strength and safety; therefore, the question must be investigated and settled in advance. The rising of the material is prevented by first removing any soft material, and further by making the dam very wide, with a thin extended toe, thus making the counterweight a part of the dam itself. Even with the greatest precautions a slip in the rock fill due to giving way of soft material near the old French canal occurred and caused great popular alarm, and led the President to order a board of eminent engineers to Panama. Their report was most reassuring and confirmed in the main the judgment of the commission.
Not only the dam itself, but also the material upon which it is built, must prevent the water from flowing underneath it. To increase imperviousness, the commission drove a line of sheet piling twenty feet into the earth; but on the advice of the special board of engineers this was omitted and, instead, a trench was dug along the middle, which was filled by the core of the dam.
The generous dimensions of the dam, however, principally contribute the imperviousness and stability. As finally built the crest is loo feet wide and 20 feet above normal water-level; the thickness of the dam at the water-surface is 400 feet, and it increases to a thickness of nearly one-half mile at its deepest part.
The dam, after clearing the 573 acres of site, was constructed )y first building long mounds along the outer lines of the dam wth the proper exterior slope. The material was spoil from the Culebra Cut, the locks and the spillway, and was dumped from trestles. When the mounds were carried to sufficient height, the interior space was filled with silty material from nearby deposits by the hydraulic dredging process. Where the course of the Chagres crosses the dam two lines of sheet piling were driven, and the material between them, which was not of a suitable character, was excavated and replaced.
The design of the Gatun Dam was not decided on until elaborate tests had been made of the actual seepage through the material to be used in the construction. These seepage tests were made by drilling holes into the deposits that were later to form the core of the dam, and pumping a measured amount of water into them and noting the loss and rate of flow under fixed pressures. The natural flow of the ground water through the soil was also studied. Several model dams were built and experiments made to determine the slope of the water through the material of the dam, caused by the miniature lake on one side. Test pits were dug in the deposits, and the flow into the test pits was pumped out and measured, while at the same time observations on the level of the ground water were taken in the neighborhood.
The dimensions of the cross-section of the dam were twice changed. The height of 135 feet above sea-level, as originally Proposed, was at first reduced to 115 feet, and finally to the adopted height of 105 feet. The surface slopes and width at the bottom were also changed.
GATUN SPILLWAY.
During the rainy season the influx of water into Gatun Lake will be much greater than the amount consumed, and the spillway through the Gatun Dam provides the outlet. It might have been placed anywhere on the rim of the lake and a channel to the sea constructed, but a favorable site on rock foundation was found on the line of the dam, which allowed the use of the bed of the Chagres for carrying the water to the sea. (See plan No. 2.)
The spillway consists of a concrete dam with means for overflow, and a concrete channel to lead the water away. It is a most important adjunct to Gatun Lake, for it not only will safely relieve the lake of dangerous flood-waters, but also will control the level of the water-surface, thus accomplishing the storage of a part of the flood-waters for use in the dry season. Its discharge capacity must be made equal to that of the greatest possible flood. To determine the amount of water, we must again seek information in the records of the New French Company and the succeeding records by the Americans. It is to be deplored that the old company obtained no record of the Chagres flood of 1879, known to be larger than any covered by subsequent. records. The engineers' report states that, "The maximum momentary discharge of the Chagres River at Gatun is calculated from the measured Bohio discharge to be 182,000 cubic feet per second." This is over 200 times the minimum dry-weather flow.
An overflow type of spillway to carry off this amount of water would be over 2,000 feet long, and even so its discharge capacity at the highest floods would not be sufficient, and the lake might rise five feet. For these reasons the commission adopted a spillway with a crest that is semicircular in plan and has fourteen openings cut through the upper part, closed by gates. The elevation of the bottom of the openings is at 69 feet above sea-level, or 16 feet below the normal level of the lake. Each opening is about 45 feet wide. They are so wide, in fact, that the top of the spillway is really composed of a series of piers, with the openings containing the valves between them. When the gate is shut, its top is at elevation 88 above sea-level, making the gate 19 feet in its vertical dimensions. The gate may be raised 222 feet, or clear of a 9o-foot depth of water in the lake. This device for discharging water from the lake is far superior to the plain crest without gates, because the amount of water passing through may be very nicely controlled; furthermore, any increase in the depth of the water in the lake from sudden floods would tend to increase the capacity of each opening of the spillway, because the amount of water discharged through a weir is dependent upon the head or elevation of water which is acting on the weir.
When the lake is at elevation 87 a single gate will discharge 11,000 cubic feet per second, or 154,000 cubic feet per second for the lot. The maximum known flow of the Chagres is less than this amount; in fact, is only 137,500 cubic feet for any prolonged period, such as 33 hours. The momentary discharge may be much greater than this and has been determined as high as 186,000 cubic feet per second, but, in designing a spillway, the momentary maximum is not what is wanted. Should any flood occur which will exceed the capacity of 154,000 cubic feet per second, then, of course, the lake will begin to rise; but as it rises, the capacity of the spillway is increased until, with the lake at the improbable elevation of 92 feet, above which the water would flow over the miter-gates and into the locks, the rate of discharge of the crest will be 222,000 cubic feet per second. In addition to this, water can be passed through the lock culverts both at Gatun and Pedro Miguel. The length of the period over which records of flow of the Chagres are available is insufficient to predict with any degree of certainty the probable maximum flood at some future time, and the commission has again shown its wisdom in designing for a capacity which is quite far in advance of that required by recorded floods.
The gates themselves are constructed of heavy and massive steel work. They are of the so-called Stoney gate-valve type. The sliding frictional resistance of ordinary valves of this size would be very great. The Stoney pattern of valves overcomes this by using roller trains upon which the valve travels. Passing lengthwise along the dam and underneath the gates is a tunnel in which all the machinery for operating the gate valves is placed. A chain is fastened to each side of the gate and passes over a sprocket-wheel on the adjoining pier, and then down through a vertical well to the machinery tunnel. A large screw is fastened to the end of the chain and passes through a worm. A heavy counterweight hangs on the lower end of this screw rod, leaving only frictional resistance to be overcome. The motor for operating the worms is located midway between the screw rods, thus applying equal lifting force to each end of the gate.
After passing over the crest the water slides over the face of the spillway, which is so designed as to fit the normal curve of the water. At the bottom the concrete work is curved so as to give the stream a horizontal direction. About 21 .baffle piers are built within this area to retard the rapid flow. At the same time, the channel becomes contracted from a width of 414 feet, which is the length of the inside of the crest, to a width of 285 feet. The water is carried in a long sluice-way, lined with heavy concrete walls and paved with a concrete floor, and is discharged at a safe distance from the dam into the bed of the Chagres River, whence it continues to the sea. During the dry season of four months very little wafer will pass through the spillway, but in the rainy season varying amounts will pass. The average flow will be about 10,000 cubic feet per second, increased momentarily to almost 15 times that amount during periods of high flood. Over the tops of the piers which separate the gate openings a bridge and roadway have been built, so that traffic may be carried the full length of the Gatun Dam.
So important to the success of the canal is this spillway that the commission's engineers constructed a model of the same for experimental purposes, 1/32 of the size of the original. It was tested under various conditions and the facts thus gained were of value in making the final designs.
EXCAVATION OF CULEBRA CUT.
The Culebra Cut is very generally and very justly considered the most important part of the canal construction work. (See plan No. 5). The date of completion of the cut practically determined that of the whole canal. It was in charge of the Central Division of the canal organization, which covered also the small amount of dredging and excavation within the limits of Gatun Lake. Total expenditures are a good measure of the magnitude and relative importance of the various items and are given in the table below, showing that over half the amount applied to construction work direct, was for the Culebra Cut. There might be added to the total for the Culebra Cut $20,000,000 of the payment for the French property which applied to excavation, thus indicating that the cut comprised over 55 per cent of the construction work of the canal proper.
TOTAL EXPENDITURES TO JUNE 30, 1912.
DIRECT CHARGES TO CONSTRUCTION.
Atlantic Division: Channel Gatun to sea; Gatun Locks, Dam and Spillway; Colon Breakwater, etc $43,875,000
Central Division: Culebra Cut 76,565,000.00
Pacific Division: Pedro Isdiguel and Miraflores Locks, Dams and Spillway; dredging Miraflores to sea; breakwater, etc. 31,710,000.00
EXPENDITURES NOT CHARGEABLE DIRECTLY TO CONSTRUCTION.
Department of Sanitation $14,815,000.00
Payment to French Company 40,000,000.00
Payment to Panama Republic 40,000,000.00
Panama Railroad improvements and relocation 13,650,000.00
Steamers purchased and repaired 2,680,000.00
Zone water-works, roads and improvements 7,600,000.00
Canal Zone buildings 10,135,000.00
Miscellaneous items 8,070,000.00
Total to June 30, 1912 $260,000,000.00
A typical American tool developed largely on railroad work, namely the steam-shovel, solved one of the vital parts of the excavation problem. Its function was to pick up the soft or blasted hard material and place it aboard the cars. It performed its function so well that the rate of progress was dependent on keeping the shovels supplied with cars and disposing of the material on the dumps. Again allowing the cost of the various items into which excavation may be analyzed to indicate their relative importance, the following table, taken from the records for the fiscal year 1912, is given with the items arranged in the order of cost.
ANALYSIS OF COST OF EXCAVATING CULEBRA CUT, TAKEN FROM RECORDS FOR FISCAL YEAR, 1912.
Cost per Cubic Yard.
1. Transportation $0.1331
2. Drilling and blasting 0.1157
3. Tracks 0.0885
4. Loading by steam-shovels o.o68t
5. General expense and supervision 0.0503
6. Dumps 0.04.79
7. Plant, arbitrary 0.0395
8. Drainage, structures and clearing 0.0045
Total unit cost $0-5496
The clearing of the site in preparation of excavation work was of minor importance. After the loose material had been cut away by the shovels, the drilling and blasting followed. Of the total of 93,000,000 cubic yards of material removed from the cut prior to July 1, 1912, about 66,500,000 cubic yards, or 7 1/2 per cent, required drilling and blasting. The power for drilling was supplied by a large compressed-air main, which was tapped at convenient points and the lines laid to the drills. The work was most carefully studied and planned. Systematic records were kept of the amount drilled by each crew daily. Familiarity with the material and trial of various methods indicated exactly the setting of the holes and the depths to which they should be drilled to obtain the greatest economy. All loading of holes and firing was placed in the charge of a special crew of trained men, and the firing was done by current from the electric station at Empire. There was a serious accident during the early stages of the work, due to a premature discharge of a vast quantity of dynamite that had been placed in the holes and left there for firing at a convenient time. From some obscure cause, such as the overheating of the dynamite, it exploded and killed a large number of men. Thereafter the dynamite was fired within a few hours after being placed, with the result that in three years only eight men were killed by dynamite, although a total of 19,000,000 pounds of explosives was used in the Central Division during that time. A knowledge of the handling of explosives, as in the case of many "other important public works formed an asset of great importance. Various kinds of explosives were used, including saltpeter dynamite with 6o per cent nitroglycerin, saltpeter dynamite with 40 per cent nitroglycerin and Trojan powder. The total amount of explosives used on the entire canal work to June 30, 1912, reached the enormous total of 50,000,000 pounds. When the blasting did not break up the material small enough for handling by steam shovel, it was further broken up by so-called "dobe" shots, which consisted in laying a small stick of dynamite on the top of the rock and detonating it with a safety fuse.
The shovels worked on short pieces of track, which were extended as the work progressed, while the cars for receiving the material were handled on parallel tracks next to the shovel. So rapidly did the shovels load cars that the handling of dirt trains into and out of the cut was a problem in railroad transportation of the very first order. Within the limits of the cut there were nine parallel tracks to carry the traffic, having a total length of over one hundred miles. Where two or more shovels were working on one line, the empties came in on one end of the track, so that each shovel had a train of cars. As soon as any shovel filled its train, all were immediately shoved ahead so as to get the full train out of the way. By adhering to this system the first train was always the one to he loaded first. All trains were handled by a train despatcher and his assistants, who were located in a tower in a commanding position and provided with telephones, flags, and other forms of signalling apparatus. A great deal depended on the manner in which the train despatcher handled his work. There were empties to get into the cut over a complicated system of tracks to a proper shovel; there were loaded trains to be moved on, and loaded trains to be passed out of the cut; there were workmen's trains, accident cases, special locomotives, and other traffic to handle. There was scarcely a moment when some definite action, affecting the economy of the entire operation, was not expected of the train despatcher. The trains were passed on to the construction tracks and thence to the main line of the Panama Railroad. The dirt trains invariably had the right-of-way. To observe the work of these train despatchers, and to see the constant procession of dirt trains and empties rolling along the main line of the Panama Railroad, was most impressive. The traffic was probably equal to that on the main lines of a great many of the important trunk lines of the United States. The amount of traffic is indicated by considering the average number of locomotives and cars in use during a typical year, namely 1912, as shown by the following table:
LOCOMOTIVES AND CARS. Average Daily Number in use, 1912.
Locomotives handling spreaders 6
Locomotives handling unloaders 10
Locomotives handling track shifters 3
Locomotives handling dirt and miscellaneous trains 117
Lidgerwood flat cars, average per day 2403
Large steel dump cars 320
Small steel dump cars 973
The largest number of cars handled in one day during the year 1912 was 4896. In other year's the amount was even larger. The number of shovels in use during this year was 46, of which nearly half were 95-ton shovels with a dipper capacity of 5 cubic yards. The highest daily yardage for one shovel was 4465 cubic yards. The highest annual record was 543,481 cubic yards. The average amount of material handled per shovel per hour increased from 1.21 cubic yards in 1908 to 165 cubic yards in 1912. In the meantime the average cost per cubic yard of excavation dropped from $0.725 in 1908 to $.0.55 in 1912.
The disposal of the excavated material required most careful thought and involved considerable engineering ability. The rate of progress on the Culebra Cut, and therefore the rate of progress on the whole canal, at various times depended upon the speed at which the trains could dispose of their loads of dirt. Where the material could possibly be of any use, trestles were built and the material was deposited without rehandling directly where it was needed, as in the Gatun Dam, the back fill behind the lock walls, the embankments of the new Panama Railroad, and in raising the level of swamp lands, making land, and building a breakwater at the Pacific entrance of the Canal. The vast bulk of the material was wasted. The principal dumps were at Tabernilla, Gatun, Miraflores, Balboa and the Panama Railroad relocation. Each of these dumps took from 5,000,000 to 18,000,000 cubic yards. Trestles were first built to dump material off the cars; and as the level of this fill rose, the track was removed from the trestle and shifted always toward the edge of the bank. It was the constant shifting of track and extension of trestles which caused the delays in disposal of material. The ingenious methods that had been developed on railroad work and elsewhere were utilized on the dumps. A small amount of the material was handled in steel side-dump cars which landed the material alongside the track. Air-pressure from a locomotive was used in dumping these cars. Another and a more ingenious method for unloading them was by means of a large plow. The cars were flat and had a bulkhead on one side only; to balance this the other side overhung slightly more. When a train arrived at the dump an enormous plow of the full width of the car, was set on one end of the train, and a cable led to the other end. The winding of the cable drew the plow the full length of the train and discharged all the material on to the ground next to the track.
A further operation was necessary, because the track could not be laid directly on the brink of the dump. The material which was piled up by the dumping of the cars was shoved off the edge of the embankment by means of an enormous plow suspended over the area alongside the track from a special car, and pushed along by powerful locomotives. When the dump had been widened to a point where the plow or spreader could no longer slide the material out of the way, it was necessary to shift the track. Here again railroad experience was brought into play, and the work of hundreds of men was done by a small crew with a track shifter. This machine had two booms; the first lifted the track off the ground, the second was slewed, and a line passing over it was made fast to the track and drew it into its new location. The length of the booms was sufficient so that the weight of the shifter itself, which ran on the track did not affect the work.
Special problems were encountered in some of the dumps, of which one of the most interesting was the disposition of silt and clays taken from the Chagres section of the Central Division. It became very soft when exposed during the rainy season, and the slope was found to be in some cases as flat as 1 vertical to 22 horizontal. It was impossible to maintain tracks on such material. Accordingly, a track was laid along the banks of the Chagres on hard ground, and when the material was dumped it was thoroughly wetted by means of a 4-inch water-pipe, whereupon the saturated material slid slowly but firmly into the Chagres River. The current was sufficient to carry it along and deposit it at points where it could do no harm.
GEOLOGY AND THE SLIDES.
The material through which the Culebra Cut passes is very variable. The region of the Isthmus was once geologically very active, and each period of activity is marked by material typical of the conditions under which it was formed. Fortunately, as in so many other parts of the world that were once the scene of geologic or volcanic activity, the Isthmus is now in a quiescent period and the great geologic forces are in a condition of stable equilibrium. When the canal project was being agitated there was great apprehension on the part of those not familiar with conditions as to possible volcanic eruptions or earthquakes. In allaying this feeling, the photographer of the flat arch in the ruins of the old Santo Domingo convent in Panama played a very important part. The fact that the arch has stood for so many years, while the roof and windows have disappeared and the masonry has deteriorated, adds to the impressiveness. Equally important, as proving the absence of seismic disturbances, is an almost exactly similar arch in a nearby church which still carries its superimposed floor load. Being in a different plane adds to the force of the evidence.
The comparatively infinitesimal forces controlled by the hand of man in a few localities produced minor conditions of instability that have resulted in so-called "slides" or "breaks." Fortunately man controls the means to restore equilibrium. This phase of the canal work will be more fully described later on.
From the reports of the commission's geologist it is learned that the oldest rocks are exposed along the canal from Bas Obispo, not far from the head of Gatun Lake, to Empire, about the middle of the Culebra Cut. These are of a character known as basic metaconglomerates overlain by a series of miscellaneous volcanic rocks. The whole in past ages has been under heavy stresses, which have caused faults and sheers; that is, the rocks have cracked and the parts have slid by one another vertically, and this resulted in very much broken masses. From Empire to Paraiso, at the head of Miraflores Lake, and thus including the rest of the Culebra Cut, there existed in a former age a great basin or sag. The rocks which compose the sag or downwarp are soft and friable in their layers, and consist of carbonaceous clays and shales, with intermixture of pockets of gravel, sand and marl. This basin no longer forms a valley, for during succeeding geologic periods it was filled with new formations. The carbonaceous basin rocks are overlain by the next younger formation, composed of light gray limy sandstones and sandy limestones in beds or lenses, and separated from each other by thin beds of friable shale with occasional masses of carbonaceous matter. These formations contain fossils of marine fauna which also occur at other points entirely across the Isthmus, and as these are formed only in the shallow estuaries of the sea, it is proven that the materials in which the fossils are now lodged were deposited under water; and their disposition across the Isthmus is considered by geologists as proof that the Atlantic and Pacific Oceans were joined at that time. The latest marine-deposited rock is composed of coral and shell limestones and is of non-continuous occurrence. During succeeding ages these formations slowly rose as they are now above the level of the sea. There was then aerially deposited a thick bed of greenish finegrained volcanic clay rock, which fills the depressions in the marine-deposited rocks—the remains of probable former estuaries and channels. This deposit is also not uniform, but contains beds of gravel, sandstone and lava flow. The whole is weak and crumbly.
The most recent geologic formations consist of masses of volcanic rock; molten lava from below, forced its way through the softer rocks along the lines of least resistance, sometimes spreading between the layers of softer rock and sometimes breaking through in great rifts, forming dikes. Great volcanic masses have also risen, due to the pressure exerted from below, and, forcing their way upward in a cold condition through several hundred feet of softer overlying rocks, are said to have formed such elevations as Gold Hill and Contractors' Hill.
The geologically recent volcanic rocks are generally hard, and they fortunately serve to greatly strengthen the banks of the canal. The various rocks are in irregular formation, and have in some cases been dislodged from their former relative position by faults or vertical sliding of unstable masses, and by the breaking and cracking into blocks of masses of contiguous rocks. The older rocks are in general of a weak character, easily crushed and weathered.
With this brief description of the local geology, the problem ahead of the engineer in planning and making the Culebra Cut becomes a little clearer. It is to be remembered that most of the information now available was unknown .before the excavation exposed materials hundreds of feet below the surface. Where the canal passes through a deep cut, the exact slopes to be given to the sides are of the greatest importance. If they are too steep the material will slide or fall into the canal, and if the slope is flattened even a little, unnecessary excavation and greater cost will be incurred, increasing rapidly with the depth of the cut. The side slopes must be determined in advance of excavation, as far as possible, because the shovels in the beginning cover the full width and gradually work to the lower levels. The cutting of any additional material from the side to flatten the slope will be hazardous and costly. As the cut progressed, the bulk of the side slopes proved stable. But as already mentioned, certain areas of instability developed into breaks and slides.
The slides are a feature of the canal operations that has received perhaps more than its share of attention, and has been made use of by alarmist press agents. Whereas the amount of excavation for the whole canal is 212,227,000 cubic yards, the total additional amount of material to be removed, due to the slides, is estimated to be approximately 20,266,000 cubic yards, or less than 10 per cent of the total excavation, or a little over 16 per cent of the dry excavation or about 20 per cent of the excavation in the Culebra Cut. This is relatively the same condition that would be encountered on an ordinarily difficult sewer or water-pipe trench. Recent activity of the slides will increase the amounts.
The slides are not to be minimized, however, as the amount of material involved is equivalent to the excavation for 6o of the largest dry docks. Careful attention has been given them by the commission, and the geologist employed by them has made a thorough examination and report on the subject.
Slides have developed at those points where the side slopes of the canal excavation were left too steep; that is where not enough material was taken out to provide a stable bank, having in view the soft or weakened character of the material. By removing additional material, stability of the banks results and the slides are thus resolved into a problem of the ultimate amount of excavation. Very large areas are involved. The Culebra slide for instance covers 46.6 acres and involves the excavation of over 7,000,000 cubic yards. The Cucarache slide covered over 47 acres and involved over 3,000,000 cubic yards. These are the largest.
The slides are of four different characters, each due to different conditions. The first is produced where a bed of clayey materials, with or without superimposed formations, rests on a bed of harder material which pitches toward the canal. If the surface is sufficiently lubricated by the ground waters, the superincumbent mass slowly moves into the canal. The second class results where faults or great geologic cracks in the rocks occur, and where the fault is at such an angle that the material in the canal prism held the rocks from sliding and, upon excavation of this material, there is nothing to prevent a sliding into the canal. The third and most subtle and difficult form of slide, which is locally known as a break or structural break, begins by a vertical settling of the banks. Cracks form and the material between cracks settles a little more on the side toward the canal, causing the cracks to open and -a series of steps to form; at the same time the bottom of the canal rises. The rocks in which this phenomenon occurs are some of the weakest in the canal and are composed of loosely cemented rounded particles, Very little stress will break the cementitious material, and the rounded particles then flow freely on one another; there is nothing to prevent their sliding, as would be the case if they interlocked like pieces of broken stone. The masses do not slide directly into the canal, but the high part of the bank drops vertically, slides some, and forces the bottom of the excavation to rise. It reaches a state of equilibrium by a different method than the normal sliding mass. The fourth form of slide is that due to erosion and weathering induced both by physical and by chemical forces. Just as every cliff has as its foot a talus of broken bits of weathered rock, so the banks of the canal will weather, and limited amounts of material will wash into the canal. Vegetation will retard this. The rest will have to be dug or later dredged from the canal.
The serious problems of the slides will have been solved when the canal is finished. No one can predict with certainty, however, that they will have been altogether eliminated by that time. New slides may develop or old ones extend. But the slides are usually slow to develop, and the material can be rapidly excavated should any occur. The commission will no doubt leave for the maintenance force a fleet of dredges and other excavating apparatus, with which the problems could be met should they arise.
It may be added that it is most fortunate that we did not adopt the sea-level canal, for with 85 feet greater depth the slides in the cut might easily have been fourfold the present extent, and they might indeed have been a problem of the first magnitude.
MIRAFLORES LAKE.
Miraflores Lake is a very much smaller body of water than Gatun Lake, and lies between the locks at Pedro Miguel and those at Miraflores. (See plan No. 1.) It is a little over 1 1/2 miles long and about 1 1/2 miles wide at its widest part. It was at first intended to have the lower locks built close to Balboa instead of at Miraflores. If this had been done, the lake would have had an area of 7 square miles instead of as built, only one square mile, and would have afforded a very fine navigable channel of 5 miles, instead of only 1 1/2 miles, as at the present time. This was the scheme proposed by the Board of Consulting Engineers in their report of 1906. The change from the board's plan to the one finally adopted involved an increased cost of about $10,000,000.00, and was apparently disadvantageous, so far as the physical characteristics of the canal are concerned. The reasons for the change were that close to Balboa the locks would be subject to hostile gun-fire from the Bay of Panama, and that the preliminary work on the dam at Balboa connecting with Sosa Hill showed that the most suitable foundation did not exist.
The water-level of Miraflores Lake will be carried at elevation 55 feet above mean tide. Miraflores Lake occupies a portion of the valley of the Rio Grande River, and at its lower end the Miraflores locks have been constructed in the line of this valley. Dams extend from the lock walls to neighboring hills, which are close by, so as to enclose the lake. The dam on the west side of the locks makes an apparently unnecessary sweep to the south, but the object is to capture the flow of the Cocoli River for use in the lake and to prevent the water from giving trouble in the valley below the locks. The flow from the Rio Grande and Pedro Miguel rivers, and one or two other smaller streams, also enters the lake. The water from Gatun Lake which is used in the single lock at Pedro Miguel will flow into Miraflores Lake. The water consumption from Miraflores Lake is that due to evaporation and lockages through the two sets of locks at Mirafibres, and the amount used will be in excess of the supply from the rivers during the dry season. The difference will be made up from water allowed to flow into Miraflores Lake from Gatun Lake. During the rainy season there may be an excess of water, and this will be discharged through a spillway having, gates exactly like those for the Gatun Dam spillway. The capacity of the gates was not, however, designed from the estimated flow thus obtained, but was based on the flow which would enter Mirafibres Lake in case all the gates in one of the Pedro Miguel locks should be wrecked, and the full head of water from Gatun Lake should flow uninterruptedly through one of the Pedro Miguel locks. The discharge from the spillway is into the old channel of the Rio Grande River, over which the spillway is built. After following the old channel for about one mile, the water will be carried through the Rio Grande diversion for about 1 3/4 miles, when it will again enter a part of the old river channel and find its way to the sea close to the mouth of the canal.
THE CANAL LOCKS.
The passage of a vessel through locks wherein it remains continually water-borne is comparatively simple, as 'compared with the usual process of placing vessels in dry dock, involving the removal of water from the dock and support of the ship on blocking. The percentage of accidents in both cases is found to be exceedingly small. About 90 per cent of the accidents in locking vessels is due to failure of signals from the bridge to the engine room, and these will be eliminated at Panama through the adoption of a part of the process in common use in docking; namely, the vessel will not move into the lock under its own steam but will come to a full stop at the approach wall, and the movement of the ship will then be controlled by the lock operatives. Two lines to the bow and two to the stern will be used, the strains being obtained from four electric locomotives with winches on board, running on rack railroads on the edge of the lock walls, two on each side of the lock. For large ships more lines and more locomotives may be found necessary. The process is not dissimilar to towing canal boats, but with amplifications. With experience there will no doubt be developed the proper order of seamanship to handle vessels expeditiously under these novel conditions. (See plan No. 6.)
The canal has in all twelve lock chambers, two flights of three each at Gatun, two flights of one each at Pedro Miguel, and two flights of two each at Miraflores. The twelve locks are alike in their principal features, but variations occur from differences in arrangements of gates and protective devices. The lock chamber must have at least one gate at each end, to separate it from the adjoining chamber or from the adjoining body of water. The minimum number of gates that would fulfill this condition for the arrangement of locks adopted is 18. The actual number used is, for various reasons to be explained later, increased to 46.
Each lock has a chamber Ho feet wide and moo feet long, but as about 95 per cent of all ocean-going vessels are under 600 feet long, the locks are divided by a second set of gates into two Parts, one 400 feet long and the other 600 feet long. There is no saving of time in filling a small chamber rather than the full t000-foot lock, since all filling is done at the rate of 2 feet per minute; but advantage in the use of divided locks arises from the great saving in water, which is an element of importance, as we have seen in considering Gatun Lake. This feature adds ten pairs of lock gates to the installation. One duplicate lock, namely the lower one at Miraflores, is not provided with the dividing gates. This is because the designing engineers found that the cost of the gates and additional length of concrete structure in this particular lock, due to tidal conditions, outweighed the saving in water.
Should a vessel approaching the first lock of any flight not come to a stop through some misunderstanding, a collision with the lock gate will be prevented by a chain of 3-inch iron stretched from one side of the lock to the other. The impact will be taken up by hydraulic cylinders in the lock walls to which the ends of the chain will be attached. The resistance is sufficient to stop a 10,000-ton vessel .moving at 4 knots per hour in a length of 73 feet- When not in use the chain will rest in a groove in the floor and side walls. If the chain should give way, or not be in position, the impact would be received by a pair of guard or safety gates, which it is expected would check the vessel and prevent it from injuring the next set of gates. Should the inconceivable accident happen of a vessel passing both the guard chain and safety gate and wrecking the next one while all the other gates in the lock were open, due to a vessel having just passed through, then Gatun Lake would begin to flow out to the full capacity of the channel now formed by the lock, and similarly for Lake Miraflores. Four guard gates are required to protect the entrances to the four lock chambers adjoining Gatun Lake at Gatun and Pedro Miguel, and four more to protect the exits from the same locks, as an accident at the exits would have the same consequences as at the entrances. Similarly, two gates each are required at the entrances and exits of the upper Miraflores lock chambers, or a total of twelve guard gates.
A guard gate is also constructed at the lower entrance of each flight of locks, and the leaves of this gate point away from the lock. Each of these gates is a guard for vessels approaching from below snd also may be used in unwatering the lock.
Even the well-nigh impossible combination of circumstances described above would not wreck the canal. The mitering lock gates could of course not be closed against the flowing stream, and to stop the flow the emergency dam would be brought into play. The emergency dam is in the form of a bridge resting on a turntable on the side wall of the lock. It may be turned so as to span the lock and then be firmly bedded on each side. A series of steel girders with the upper ends fastened to the bridge would be lowered by cables into position, having the lower ends on a concrete sill provided for the purpose. Then steel plates would be forced down one by one, supported by the girders, and the opening would thus be gradually closed by a steel wall and the flow practically stopped. A floating caisson such as is used with dry docks would then be placed at the lake end of the lock on a seat provided for the purpose. The caisson carries a pumping plant for unwatering the lock, and repairs may thus be made. In the meantime traffic would use the other series of locks in both directions.
The locks are some of the most massive concrete work in the world. The dividing wall between the flights of three locks at Gatun, with the approach walls which are in extension of the dividing wall, forms a mass of concrete 6o feet thick, about 81 feet high, and over 1 1/8 miles long. The approach walls are of cellular construction. The dividing wall is built with the faces vertical and is solid for over half the height. Above the solid portion the center of the wall is filled with earth, except three superimposed tunnels. The lowest tunnel is used for drainage of the upper ones, the center tunnel for electric light and power cables, and the upper one as a passageway for employes to reach the various chambers containing machinery for operating the miter gates and the many valves. The exterior walls of the locks are of equal height with the central wall, and are from 45 feet to 50 feet thick at the floor-level; they diminish by steps on the back to a thickness of 8 feet at the top. The thickness of the floor is variable but is approximately 13 feet.
The emptying and filling of the locks is done through circular openings in the floor, each 3 feet 10 7/8 inches in diameter and having an area of 12 square feet. There are five of them in each line across the lock, and the lines are spaced 32 feet to 36 feet apart. In one moo-foot lock there are in all 105 openings with a total area of 1260 square feet. Each row of five openings communicates with a cross-tunnel under the floor. Eleven of these cross-tunnels in each lock lead to the outside wall and there open into a culvert 18 feet in diameter, without the interposition of valves. The remaining ten tunnels, alternating with the others, lead to the center wall where a cylindrical valve allows each tunnel to communicate with the culvert in the center wall, which is also 18 feet in diameter. The center-wall culvert receives the tunnels from both locks. It extends the full length of the three locks at Gatun, and at the upper end it opens into Gatun Lake, while the lower end discharges into the sea-level canal. There are control valves at each end and also in the line of the culvert at intermediate points corresponding to the locks. It is evident that, with a proper adjustment of the culvert valves, the water in any two lock chambers may be equalized by opening the cylindrical valves that allow the floor tunnels to communicate with the center culvert. This allows a very considerable saving of water in operation. With all culvert valves open, the center culvert may be used to discharge water from Gatun Lake into the sea. The side-wall culverts also extend the full length of the locks, and have control valves at the ends and at points corresponding to the ends of the locks, and at the subdivision points. They may be used in equalizing the water in any two locks that adjoin endwise, or in passing water into and out of the end locks. (See plan No. 6.)
LOCK-OPERATING MACHINERY.
All machinery connected with the locks is operated by electricity and has been specially designed for the canal work, based largely on previous experience with locks. There are 114 rising stemgate valves, 120 cylindrical valves, and 92 machines for operating the individual leaves of the large miter-gates. The apparatus is equipped with remote control and position indicators, 'which show at the control switchboard the positions of the gates and valves during operation. Indicators also show the various water-levels. All regular operating machinery will be controlled by means of interlocking switches, with one central switchboard for each of the three groups of locks at Gatun, Pedro Miguel and Miraflores. There is also local control and hand operation where feasible. The whole installation is a good example of electric operation.
Realizing that a great deal of the machinery was of new type and that the operating conditions in a tropical climate would be unusually severe, the greatest care was exercised before finally deciding on the type and character of the apparatus. In most cases a sample piece was first made and actually tried out under the severest working conditions, and changed if necessary before the order for the whole lot was given.
The cylindrical gate valves controlling the tunnels from the center-wall culvert consist essentially of a vertical cylinder placed in a chamber adjoining the culvert. The cylinder is seated at the bottom, and directly beneath it is a well to the floor culvert. A short lift gives a large waterway under the edges of the cylinder.
The great advantage of the cylindrical type is that it is very quick-opening, and that the water pressures are balanced and do not tend to prevent either opening or closing. On the canal a special form is used which does not involve carrying the full diameter of the cylinder above the water-surface.
The larger openings to the main culverts are controlled by rising stem gate valves of the Stoney pattern, similar to those used in the crest of the Gatun spillway dam. The gate is made of heavy structural steel, and the water-pressure is taken by a train of rollers at the back of the valve upon which the gate moves. Leakage is prevented by means of a metal water-seal extending around the face of the valve. This seal is fastened to the valve and slides on the wall of the opening and forms the only sliding friction of the whole valve.
Each mitering lock gate consists of two leaves hinged to the walls at opposite sides of the lock, and each leaf is 65 feet long; that is, longer than half the width of the lock, so that when the two leaves are closed, they form an angle pointing against the water-pressure. The 92 leaves weigh in the aggregate 60,000 tons, a weight in excess of that of two modern dreadnoughts. If all the gates were laid flat in a pile, it would be 644 feet high.
The joints at the hinges are made watertight by means of Babbitt metal. Embedded on the sill of the lock is a heavy block of wood, against which a similar block along the lower end of .the gate fits. The water-tight joint, however, is made by means of a seal on the under side of the block on the gate in the form of a rubber flap 1/2-inch thick, which is forced against the seat by the water pressure itself. The weight of the gates is decreased by watertight compartments near the bottom, which give, flotation. A trunk extends from the deck to these compartments. Some of the upper water-tight chambers may be filled so as to control the buoyancy of the gates for different levels of water. When in motion the gates hang simply on their hinges, and there are no rollers on the floor of the dock.
CONSTRUCTING THE LOCKS.
In deciding on the site for the locks extensive and elaborate borings were made, indicating the exact character of the material. In every case a rock foundation was selected.
The Gatun Locks were constructed somewhat earlier .than those at Pedro Miguel and Miraflores, and the method of building them also differed from that used for the others. The conditions were not so favorable for economical work. The three Gatun locks and the approach walls contain over 2,000,000 cubic yards of concrete. For purpose of comparison it may be stated that a large modern dry dock contains less than one-tenth this amount.
The broken stone was obtained from quarries at Porto Bello, which were opened particularly for the lock work. The material was quarried and crushed at Porto Bello, and was transported on barges in tow of commission tugs and carried through the old French canal, which happened to pass very close to the site selected for the locks. On account of the silting in of the old canal and the long haul, the cost of transportation was quite materially increased. The cost of the stone delivered at Gatun, including cost of plant and overhead charges, averaged $2.40 per cubic yard. The sand was dredged at Nombre de Dios and similarly transported on barges, at a total cost of about $2.10 per cubic yard. Cement was shipped from the United States to Colon, transferred by train and placed in storehouses at Gatun. The mixing of the concrete was done at a stationary mixing-plant. The stone, sand and cement were transferred by gravity, in proper proportions for each batch, to cars which dumped the materials into the mixers. After thorough mixing, the concrete was discharged into buckets on electric cars which ran on an automatically operated electric railroad. The cars were carried to tracks parallel to the locks and were stopped at the proper point. To transfer the concrete to the desired location in the lock, a number of aerial cableways were used, extending from one side to the other of the locks. The cable at one end was fastened to the top of a movable tower which contained hoisting apparatus, and at the other end the cable was fastened to a tower that was also movable but contained no machinery. The concrete was lifted from the cars, and by trolley operating on the cableway was carried over the point of deposit, lowered and dumped.
The forms for the interior face of the side walls consisted of a heavy steel frame with steel face plates which were moved into position. The full height of the wall for the length of the form was then constructed, whereupon the form was moved to the next section. The cost of concrete on the Gatun locks was $6.64 per cubic yard in 1911 and $7.76 in 1912.
For the Miraflores locks broken stone was brought from a very large quarry. opened high up on the side of Ancon Hill, where a satisfactory quality of stone was found. About 5,000 cubic yards of stone were turned out daily. Heavy blasts were set off above the berm, and steam-shovels then loaded the material into railroad dump cars, which were switched farther down the hill by locomotives to the top of a crusher, and were dumped directly into it. "Dobe" shots were fired off in the cars to split the stones which were too large. The crusher could take stones equal in size to that of an ordinary chair. The crushed material was screened, and that of proper size was carried by rubber belt to a sorting-screen and passed into the storage bins underneath for the various sizes. The material from the large crusher which was rejected by the screen passed into four small gyratory crushers, and from these on to the same belt for transfer to the sorting-screen. With this efficient and well arranged plant the cost of stone delivered at the site of the locks was about $0.82 per cubic yard.
Sand for the Miraflores Locks was obtained by dredging at Chame and was transferred by barges to Balboa, where it was excavated by means of grab buckets and was placed in overhead storage bins for transfer by rail to the lock site. The total cost in storage at the locks was about $0.76 per cubic yard.
To handle the stone and sand in building the Miraflores Locks, an elevated trestle was built parallel to the locks and about 200 feet away. The cars dumped the stone on the side toward the locks, and the sand on the side away from them. On the bank between the locks and the storage pile a large cantilever crane operated on a track. The tower contained bins and hoppers and two large concrete-mixers. One cantilever arm overhung the storage piles, and a grab bucket kept the bins full. The other cantilever arm overhung the nearest lock wall and transferred the concrete from the mixers to the lock wall. The cement was taken directly from the cars to the tower without first going into storage. In the lock chamber was another cantilever crane, which transported concrete to those parts of the lock beyond the reach of the mixing-crane. The entire plant is probably one of the most perfect ever devised for handling concrete. The cost of the concrete in place was $4.68 in 1911 and $4.77 in 1912, per cubic yard.
LOCKS AS THE LIMITING FEATURE.
The locks fix the maximum-size ship that may use the canal. They will pass the largest now built or building, but will not, for instance, pass the floating dry dock Dewey, which passed through the Suez Canal on the way to the Philippine Islands. The size of the locks was determined from the provisions of the Act of Congress approved June 28, 1902, which states: "Such canal shall be of sufficient capacity and depth as shall afford convenient passage for vessels of the largest tonnage and greatest draft now in use, and such as may be reasonably anticipated)…
In considering the limiting dimensions of the locks, and thus. of the canal, it must be borne in mind that there has been a steady increase in the size of ships, upon which great emphasis has been laid. If curves are plotted to show the growth in length, width, depth and tonnage, especially if the maximum ship of each period is taken, and if these curves are extended to show future developments, the predictions are alarming. However, when the curves are produced beyond a certain point other factors - not hitherto considered, and having no influence on the curves as plotted, are likely to enter. Shipbuilding has undergone an almost untrammeled development; building facilities, capital and cost have seemingly not retarded growth. Harbors have been deepened, channels have been widened, wharves, docks, locks and wet basins have been increased in size, to make way for the leviathans. The impetus toward larger vessels has undoubtedly been from economic reasons. Shipowners have found that with the larger and better equipped ships, having in view passenger traffic and advertising effects as well as freight, their ratio of income has increased and there has been nothing to curb their efforts. Communities and governments have, in their striving for all-important commercial growths, paid the bills for harbor development. As economic conditions have brought about the steep rise in the shipgrowth curve, so economic conditions, but in another field, will tend to flatten the curve. There must be a limit beyond which harbor development cannot economically go, and beyond which the sum of the cost of shipping and building and the cost of construction and maintenance of port works will increase rather than decrease. It will be difficult to determine when this point is reached, especially because the same interests do not provide capital for both enterprises. There are already occasional indications that this factor is entering. The difficulty in providing for the largest ships in New York harbor, while from one standpoint a, physical one, is in the last analysis economic.
There is now no commercial necessity why the Panama Canal should accommodate the largest ships; the largest ships may be regarded as ocean ferries with fixed ports. The total estimated traffic capacity of 8o,000,000 tons can be handled in ships under 600 feet long, which comprise 95 per cent of the world's tonnage, but within the next generation the canal may become one of the elements which exercise a retardant influence on the maximum size of ships, depending on developments in the commerce of the world.
More important is the effect of the canal on the size of naval vessels. Battleships of the United States have increased in beam from 76 feet in 19oo (date of authorization) to 8o feet in 1905, 88 feet in 1908, and about 98 feet in 1912; and if this ratio of increase is maintained, the limiting beam would be reached in ships authorized in about 1915.
It is worthy of note that the locks of the enlarged Kaiser Wilhelm Canal from the Baltic to the North Sea are 1082 feet long and 147 feet wide, but the lift is very much less than at Panama.
THE SEA-LEVEL SECTIONS AND THE TERMINALS.
Limon Bay, through which the Atlantic sea-level section passes, faces directly north and is open to the northerly storms and seas, which are quite severe at certain times. Protection was necessary in order, first, that ships might enter the canal in quiet water; second, to provide a quiet anchorage; third, to make traffic in small boats feasible and safe between the shore and ships at anchor; fourth, to prevent the movement of silts and sands by the seas and the attendant dredging expenditure. (See plan No. 2.)
To give this protection, Toro Point Breakwater has been constructed, extending from Toro Point in a northeasterly direction for a distance of about 2 miles. The outer end does not quite cover the entrance to the canal. The breakwater protects the greater part of Limon Bay from the northerly storms, but the easterly portion is still exposed, especially to seas and storms from a northeasterly direction. The construction of a breakwater to close this part of the bay was postponed to await the results of actual experience with the one at Toro Point. It is probable that this breakwater will ultimately be built, as the present protection is not sufficient, especially for boating, and as the effects of wave action cause silting of the channel.
The breakwater is constructed from a trestle stipported on creosoted piles 85 feet long and having two tracks. The piles are driven by a railroad pile-driver with very heavy hammer, which can reach all of the piles fro-in either track. Stone from a Toro Point quarry is carried in cars on the trestle and dumped overboard, and forms the core of the breakwater. Porto Bello stone, which is harder and much more durable, is transported a distance of about 28 miles on barges and is carefully deposited on the exterior by means of derricks. The breakwater is 20 feet in width on top, and is built in water from 35 to 50 feet in depth. The height of the top above the surface of the water is about 16 feet. The total quantity of material placed to December 31, 1912, when the breakwater was nearly completed, was 954,500 cubic yards, at an average cost of $2.20 per cubic yard. In addition, 620,000 cubic yards of rock dredged from the canal was deposited in the vicinity of the breakwater. During the fiscal year 1912 the Toro Point rock cost $1.38 per cubic yard, and the Porto Bello rock $4.31.
A large anchorage basin is provided between Cristobal and the canal channel. The wharfage space at Cristobal is being increased. New piers are built on steel cylinders which were excavated inside by hand and gradually forced down. The cylinders upon reaching the proper depth were filled with concrete, and a superstructure was built upon them of reinforced concrete.
To complete the Atlantic sea-level section, from the outer end to its terminus at the Gatun Locks, required the excavation of over 32,000,000 cubic yards by dredging, costing over $7,600,000, or about 24 cents per cubic yard; and over 2,000,000 cubic yards by steam-shovel, costing over $1,450,000.00, or about 67 cents per cubic yard.
The Pacific sea-level section from the Miraflores Locks to Panama Bay cuts the winding channel of the Rio Grande River and then continues through the bay. The land is all very low. This channel up to December 31, 1912, when the work was well in hand, had required the excavation of over 34,500,000 cubic yards by dredging, at a total cost of over $8,5oo,000.00, or about 25 cents per cubic yard; over 2,500,000 cubic yards by steamshovel, at a cost of over $2,000,000.00, or about 8o cents per cubic yard, and in addition over 1,5oo,000 cubic yards by hydraulic excavation, at a total cost of over $r,ioo,o0o.00, or about 72 cents per cubic yard. The hydraulic excavation consisted in dislodging the earth by means of powerful streams of water and carrying the material, water-borne, to suction pumps which discharged it on the neighboring swamps. A great deal of submarine rock was excavated, partly through the use of a Lobnitz rock-breaker, which shattered the rock by dropping a heavy cylindrical shaft, and partly through the usual process of submarine drilling and blasting. (See plan No. 3.)
It was originally intended to carry the canal into deep water on the easterly side of the group of islands Naos, Culebra and Flamenco, which lie about 3 miles off shore. A study of the conditions developed the fact that the strong littoral currents carried silt in a westerly direction, and as the shores of the bay are lined with a very fine mud, this action would cause the dredged channel to fill continually. For these reasons it was decided to carry the channel to deep water west of the group of islands, and to build a breakwater or dike from the shore at Balboa to Naos Island, about parallel to the canal. The object of the breakwater was not to give protection from seas or storms, for these are unknown on the Pacific side of the Isthmus, but to prevent the movement of silt into the canal, to shut off the swift tidal currents which would carry vessels at right angles to their course, and incidentally, to provide a roadway from the mainland to the fortifications on the islands. An ample amount of material was available from the excavations in the Culebra Cut, which necessarily required disposal somewhere. The breakwater, or dyke, was built by means of a trestle of creoioted timber piles, from which railroad cars dumped their material into the water. The trestle was over three miles in length, and as stated in the annual reports of the commission, was driven for a greater part of its length in blue mud, varying from a few feet to 102 feet in depth. The mud particles are exceedingly fine, and the substance feels greasy and slippery, and has a very low coefficient of friction. The mud was not able to carry the weight of the stone dumped from the trestle, and the stone and trestle were continually sinking and shifting laterally. At one locality, the total vertical displacement aggregated 125 feet in a single year. In some cases the lateral displacement of the trestle was as much as 300 feet. The pressure of the stone was greatest when a 20-foot tide was out, and the displacements usually occurred at low water. The rock in settling caused parallel ridges of mud to rise about 8o feet from the center of the track. At one point a record was kept of the amount of material required to bring the stone fill up to a full height of 29 feet above the original bottom, and it was actually ten times as much as computations taking no account of settlement indicated as necessary. Such occurrences might have been very serious, but in this case unlimited material was available from the cut, and the total cost of the work was not excessive. In fact, the total cost of the dike up to December 31, 1912, was $300,000.00 for 1,121,000 cubic yards, or at the rate of about 27 cents per cubic yard, or about $13.00 per lineal foot. Costs are exclusive of the amount that would have been spent to dispose of the materials on the ordinary dumps.
The principal ship-repair plant will be on the Pacific end of the canal. There will be a large dry dock, equal in capacity to that of the locks, with an entrance of at least 110 feet clear width and a clear length of 1,000 feet. A smaller dry dock will also be built. The ship-repair yard is designed to afford repair facilities for all of the Panama Canal plant, and for visiting ships. It will comprise foundries, machine shops, equipment for shipfitting, woodworking, paint shops, storehouses, and all the other necessary outfit for the work that it will be called upon to do. Its general character will be similar to that of a large navy yard. The plant will be a valuable asset to the United States Navy, especially in time of war. There is at present a small dock and repair plant at the Atlantic end.
Unloading piers are being provided at Balboa in addition to the present facilities, similarly as at Cristobal. It is probable that there will be an anchorage basin near the dock yard, though rock bottom is a deterrent influence.
Two of the largest floating cranes in the world will form a part of the equipment, and these will be of the revolving type. They will have a lifting capacity of 250 tons at 22 feet reach, or 150 tons at 62 feet reach, and 100 tons at 82 feet, with a hook 100 feet above the surface of the water. Their stability will be retained under any and all conditions of loading, without shifting ballast or counterweight, except that the revolving structure will be counterweighted. The two cranes acting together will be able to lift any one of the enormous mitering lock gates.
The coaling plant at the Pacific end will have a total storage capacity of 135,000 tons, of which 75,000 tons will be subaqueous. Arrangements are made for separate storage of coal belonging to different owners. The capacity of the plant for unloading from colliers will be 500 tons per hour, and the total issuing capacity will be 'coo tons per hour. It is proposed to furnish coal by sale to passing vessels. The Cristobal coaling plant will be larger, and will have a total storage capacity of about 240,000 tons, of which 125,000 tons will be subaqueous. The capacity for unloading from colliers will be woo tons per hour, and the total issuing capacity will be 2000 tons per hour. The government will own and operate a large number of coal and oil lighters at each end of the canal. Oil storage and an oil pipeline across the Isthmus will also be provided.
CONTROL OF WATER DURING CONSTRUCTION OF THE CANAL.
One of the serious problems that arose in connection with the actual construction of various parts of the canal has not been touched on in describing items such as the locks, dams, and Culebra Cut, because it can be better treated as an individual subject. We realize that the canal is built in the valleys of the Chagres and Rio Grande Rivers, and that the route selected is the very lowest one that could be found. Knowing the character of tropical rainstorms and river floods, it needs but a moment's thought to make clear the seriousness of the problem of keeping the storm waters and the floods away from the construction work. Improperly or insufficiently controlled, these waters would have the power to destroy a great deal of what had been laboriously done.
The Culebra Cut forming the low point for many square miles of territory, and coinciding for a considerable distance with the Obispo River valley, would naturally collect vast quantities of water were steps not taken to prevent it. The course of the Obispo River was artificially changed, beginning at the point where it approached the cut. The total length of the new river channel as originally built was 5A miles, from a point on the east side of the Culebra Cut, near the foot of Gold Hill, to a point clear of the cut, and finally discharging into the Chagres River. On account of slides encountered during construction work, the Obispo diversion gave way, and the flow of the river entered the cut for 3 days, causing inconvenience and damage. A new diversion channel was constructed with great speed. That the Obispo diversion was no small problem may be noted from the fact that in six years a total of 1,200,000 cubic yards of excavation was necessary, of which nearly 40 per cent was in rock, and the total cost was over $1,000,000.00. The diversion was able to carry 6000 cubic feet of water per second. The Camacho diversion on the opposite side of the cut was similarly built.
These two diversions take waters which flow toward the Atlantic. The Rio Grande River formerly flowed through part of the area- to be excavated on the Pacific side of the Continental Divide. It was similarly diverted, and a dyke was constructed across the south end of the canal to prevent access of the river water. Keeping water out of the cut also kept out the silt which would inevitably have come down with the freshets.
The elevation of the bottom of the cut was 40 feet, which was lower than the Chagres River, and a dam was built across the cut with its crest at elevation 73 to prevent the river from flowing into it.
The natural streams being thus prevented from entering the work, it only remained to get rid of the water which originated along 8 1/4 miles of cut. This was done by means of centrifugal pumps at low points in the cut, which discharged the water over the dams. Excavation at a new level was always preceded by the cutting of a pioneer trench down the middle of the canal, in which all the water was collected and carried to the pumping stations. The summit during construction was at Culebra. Drainage to the south was carried to Pedro Miguel until August, 1911, when the flow was taken through the center-wall culvert of the Pedro Miguel Lock. The drainage to the north was disposed of by pumping.
The Chagres had no opportunity to interfere with the Culebra Cut, but had ample opportunity by virtue of its location, to threaten the work on the Gatun Dam. This problem was handled with ingenuity by the engineers. The portions of the dam not accessible to the river were constructed first. The spillway was built with its foundations on rock and with the river kept out by cofferdams and otherwise. In the meantime the Chagres River flowed through the west diversion built by the French. When the spillway, in 1911, had been constructed to elevation 10 feet above sea-level, and the earth dam well above this elevation, the channels of the Chagres were closed by carrying the dam across, and the water then flowed over the concrete work of the spillway during the rainy season. This depth kept the Panama Railroad, still on the old line in the Chagres valley, free of water. During the following season the railroad was transferred to the relocated or high line above the final level of Gatun Lake. The earth dam was continually kept at an elevation well above that of the concrete work of the spillway, and the next step during the dry season consisted of constructing 4 very large culverts in a part of the spillway temporarily protected from the flow of the water and controlled by gates. There were provisions for placing stop planks for closing the openings at some future time. When these culverts were completed, the dry-weather flow of the river was carried through them, and the remaining concrete work of the spillway progressed so long as the dry season lasted, and so long as the culverts were able to carry the flow. During the rainy season the flow was again over the concrete work of the spillway at elevation 50. Proceeding thus, the spillway was completed, and the final step, when the spillway is entirely done, consists in placing the stop planks before the entrance to the 4 culverts and filling them with concrete.
The Gatun Locks extend to a depth of about 55 feet below mean sea-level, and the water was kept off the site by means of a temporary dam to the north of the locks. This was built so that the excavation for the flare-walls might be done by dredges, as the material was too soft to hold steam-shovels. Inasmuch as the dredges could not dig the full depth of 70 feet, a small lake was formed over the area of the flare-walls, and its elevation was lowered until the dredge could reach the bottom. This lake was kept from flowing into the partially completed locks by means of a temporary concrete dam, built between the center and side walls near the lower end of the Gatun Locks.
AIDS TO NAVIGATION.
The Atlantic entrance will be marked by a light of the fourth magnitude placed on the end of the Toro Point Breakwater, where there will also be a compressed-air fog whistle and a submarine bell. The tangents in the canal will be defined by range lights. Vessels going in opposite directions will use different ranges giving courses 250 feet apart. There will also be side lights, spaced about 1 mile apart on each side of the channel. In the Culebra Cut the range lights are omitted, due to the tangents being so short and the banks too steep for placing them. There will be, instead, 35 concrete beacons at tangent points and at intermediate locations. By a system of screening, only those lights will be visible to the navigator which are necessary to define the channel where the ship may be.
The sides of the canal will be further marked by acetylene, flashing gas buoys of 450 candlepower, and intermediate spar buoys.
The range lights involved much clearing of forest growth, since the trochas are in general of the full width of the canal at the start, narrowing down to 480 feet at the rear light.
All lights, beacons and buoys will be white, and will be distinguished from one another by characteristic flashes. Gas and electricity will be used for illuminant, preferably electricity where feasible. Inaccessible lights will be operated by means of compressed acetylene dissolved in acetone.
The locks will be illuminated by means of 400-watt tungsten lamps on concrete posts, with concrete reflectors. The lamp will be 30 feet above the coping and will be screened by concrete skirts, so as to cut off the direct light rays longitudinally of the locks, thus keeping the glare out of the navigator's eyes.
SANITATION.
To regard the sanitation work as a mere contributory element to a successful culmination of the canal construction work does not, perhaps, place it upon the high plane that it deserves. Rather should we regard it as one manifestation of the great progressive movement that is now pervading civilization and that regards the prevention of disease as of more importance than its cure, and in its execution requires the cooperation of the physician, the bacteriologist, the engineer, and the administrator. The Panama Canal is undoubtedly the most marked single example the world has seen of the intelligent and thorough application of the principles of sanitation. In many other parts of the world, and for years, such principles have been applied in preventing contamination of water supplies, in the purification of sewage, in the control of epidemics and in other important sanitary measures; but none have had the opportunity to display in so marked and convincing a way the great benefits to be derived, especially with the example of the French experience for a background. In no case has more been done to educate the world in general in the need and effectiveness of the application in a practical way, under control of experts, of the scientific principles of sanitary science. We can with truth, therefore, say that the sanitary work on the Isthmus has extended beyond the confines of the Canal Zone and of canal construction, and its good effects on the whole human race rival those of the canal accomplishment itself.
The very title of the "Department of Sanitation" is indicative of the new era; in the old days there would have been a department of hospitals. The new era gives a department of health and its preservation, of sickness and its prevention and cure, and the old merely gave a department for the care of the sick.
Of some of the numerous activities of the Department of Sanitation, such as the Colon and Ancon hospitals, the system of vital statistics, the control and inspection of foods, the discovery and isolation of infectious diseases, and the handling of accident or emergency cases, we may only note in passing that all are well administered and rank with the best of their class in the world. The phases of the work which interest us more are the control of yellow fever and malaria.
The Americans in Cuba proved that yellow fever was communicated only through the stegomyia mosquito. It had been proven that malaria was communicated through another type of mosquito known as the anopheles. Knowing these facts, the fight against yellow fever resolved itself into several elements: 1st, prevent the introduction of yellow fever into the Isthmus by strict quarantine; 2d, isolate all yellow fever cases within doubly screened rooms, to prevent the stegomyia from gaining access to yellow fever germs and thus gaining the power to communicate it to others; 3d, screen all living spaces, so as to prevent access of the dangerous mosquitoes to the well; 4th, study the habits of the mosquitoes and exterminate them so far as possible, especially those having been in the presence of yellow fever. In accordance with these principles, all hospitals, hotels, dwellings and offices were most carefully screened; the yellow fever rooms in the hospitals were separated by screens from the rest of the hospital. Most careful and comprehensive inspections and studies led to the finding of the breeding-places of the dangerous mosquitoes and to the removal of the pools of water. In the cities all open cisterns and accidental lodgments for pools of water were removed. In the open country swamps were drained or filled; extensive systems of ditches were established and maintained; pools that could not be removed were coated with a disinfectant that prevented breeding; underground drains were placed to run off the water before it could ooze to the surface and form pools. Larvicide was liberally distributed on stagnant water that could not be drained; it was manufactured in concentrated form, was carried to the brooks in the mountains, and was arranged to drip automatically on the streams, so that if pools should form, the film of destructive liquid would already be there. Underbrush and grass were cut near all habitations, so that the sun might dry up possible pools and the mosquitoes be deprived of shade, and perish. Fish were tried for their destructive effect on mosquito larvae. The cities were cleaned, sewered, paved, and provided with water. In fine, no possible precaution that intelligence and diligence could devise was overlooked.
The result was the banishment of the hitherto prevalent yellow fever, a marked diminution in the amount of malaria, and generally healthful conditions accompanied by a low death-rate.
Sanitation work is expensive; the cost, to June 30, 1912, has been $15,000,000.00.
THE ELEMENTS OF SUCCESS.
A consideration of the elements to which the undertaking owes its accomplishment is most important and interesting, in order to correctly comprehend how success was achieved. It must first be admitted that fortune favored us. We did not apply our determination to build the canal to actual construction work until after the world had fully developed the mosquito theory, and Cuba had given us an opportunity to apply it to practical sanitation.
Two generations of railroad building; river and harbor improvement, water-works, and other large construction, together with the coincident growth of the great technical schools, had developed a body of engineers and constructors with the technique and capacity for conceiving and executing large works, and a strongly formed spirit of loyalty and devotion that allowed them to be welded into the nucleus of a great organization. Everywhere on the work are evidences of the standard practice developed by engineers on other undertakings and adapted to local conditions. Without these years of preliminary engineering training, the Panama Canal as built would have been impossible.
The management of the enterprise was first placed in the hands of engineers and others who had been eminently successful in great works conducted by private capital. They were undoubtedly able men and contributed enormously to the primary work, and are deserving of great credit. They had not had experience in conducting work under the many restrictions imposed by the government, and in dealing with superiors who were representatives, not of capital and business, but of the people of the United States. The large body of engineers in the employ of the United States were at first passed over when the greatest and most responsible engineering positions ever at the disposal of the government were to be filled. They had devoted their lives to the service and were now ignored. After but a short interval a change came, and the management was turned over to government engineers. The selections were made from the oldest, and, as a body, the most experienced, organization of engineers in the government service, the Corps of Engineers of the United States Army, and to a lesser extent, from the Corps of Civil Engineers of the United States Navy. The results of the work area sufficient tribute to the wisdom of the selection.
The evidence is clear that a strong national sentiment pervades the force, which lends inspiration to self-sacrificing cooperation, to hard work, and to contentment under discomforts—a sentiment intensified through isolation in a foreign land. It finds expression not only in the canal employe, but in every American who admires and looks up to his fellow citizen who has worked on the canal. This element of success is fundamental, and rarely has an enterprise given so good an opportunity for its display. It might easily have been smothered by ill-advised administration, but the organization is blessed with a leader who says that "we" are building the canal, and whose inspiration leads all to take the same view. It is remarkable to note the extent to which a feeling of loyalty to the work exists, rather than to the individual or to any division. Even a company agent resident on the Isthmus, in referring to the Pacific Division, states that "We put in 4500 cubic yards of concrete on the locks yesterday." This general feeling of loyalty in no way excludes a healthful rivalry for each crew or division to excel. The individual who would ordinarily be disgruntled or dissatisfied soon leaves the Isthmus, or he finds those feelings pushed into the background or smothered by the all-pervading spirit of loyalty to the work. The whole is an interesting psychological problem, which only a visit to the Isthmus can disclose in all its force.
In the valuation by the Americans of the French canal company's property, one notable item, though an intangible one, is missing—the value to us of the French experience, the lessons learned by them through years of bitter experience. Had we begun the canal as pioneers, it is of course impossible now to state what costly mistake we might have made or what untoward conditions we might have overlooked; there can be no doubt that the knowledge of what the French had done aided us in making up our minds what to do and what not to do. One of the greatest errors of the French, and one that contributed most largely to their failure, was that they did not realize until too late the magnitude of the enterprise.
In a material way the most valuable contributions to the elements of success were the well developed state of the art of making concrete, the perfected steam-shovel, compressed-air tools and numerous other mechanical devices.
IN CONCLUSION.
There is so much of interest connected with the subject of the Panama Canal that the most difficult problem in writing a limited article about it is to decide what to omit. The organization of the forces, the system of accounting and cost-keeping, the method of civil government, the Panama Railroad, the administration of the subsistence and storekeeping divisions, the importance of the canal to the navy, and many other subjects, offer a wealth of material—sufficient for separate essays—and are well worthy of study. All branches pertaining to the execution of the work have been studied out to a point of maximum possible efficiency, and that this has been possible is largely due to the absence of hidebound precedents and to the fact that control was left to the man on the ground.
The canal will soon be completed and begin its history as an actuality. Study and statistics throw much light upon what its commercial history will be. No one may venture to predict what momentous influence it may have in war or in preventing war. Whatever may be the detailed events in which the canal may take a part, there can be no doubt that it is one more step in the westward trend of civilization. The prophecy of sixty years ago by that farseeing statesman, William H. Seward, made in a speech in the Senate, is still in remarkable process of fulfillment:
Even the discovery of this continent and its islands, and the organization of society and government upon them, grand and important as these events have been, were not conditional, preliminary and ancillary to the more sublime result now in the act of consummation, the reunion of the two civilizations, which, parting on the plains of Asia 4000 years ago, and travelling ever after in opposite directions around the world, now meet again on the coasts and islands of the Pacific Ocean. Certainly no mere human event of equal dignity and importance has ever occurred upon the earth. It will be followed by the equalization of the condition of society and the restoration of the unity of the human family. Who does not see that henceforth, every year, European commerce, European politics, European thought and activity, although actually gaining greater force, and European connections, although actually becoming more intimate, will ultimately sink in importance; while the Pacific Ocean, its shores, its islands, and the vast regions beyond, will become the chief theater of events in the world's great hereafter?