It is fitting that we should do honor to the man who discovered the Sumner Line and thereby gave us a completely new concept of the Line of Position. This is the centenary of this important discovery. Perhaps no one person has influenced the art of celestial navigation more than Captain Sumner. Aside from his own book published in Boston in 1843 entitled A New and Accurate Method of Finding a Ship’s Position at Sea, there have been numerous books and articles written explaining and developing the concept of the Sumner Line, so clearly demonstrated by this sea captain on a voyage to England in 1837.
Who He Was
Captain Sumner was born in Boston on March 20, 1807, being the son of Thomas Waldron and Elizabeth Hubbard Sumner, who had eleven children in all. His immigrant forefather was William Sumner, a mariner, who came in 1636 to New England. Thomas Waldron Sumner, his father, an architect and a congressman from Massachusetts in 1805-11 and 1816-17.
Captain Sumner attended Harvard University where he received his A.B. degree with the class of 1826. According to class of 1826 accounts in the Harvard archives, he dipped for Canton as a common sailor, and became a captain in 1847. Here also mention is made of “a work ln navigation of great value.” In those days, American clipper ships were circling the globe and giving keen competition the British and other nations. On March 10, 1834, Sumner married Selina Christiana Malcolm, who bore him four children. There is a note of sadness in the fact that Captain Sumner, after his valuable contribution to the art of navigation, became hopelessly insane in 1850.
In 1852 in a petition to Congress his widow asked for a gratuity “in consideration of the discovery by her husband, Thomas H. Sumner, of a new method of finding a ship’s position at sea.” She further stated, “Her husband, Captain Thomas H. Sumner, whose scientific labors have been thus successful in adding so materially to the security of life and property, of all immediately concerned, is now himself hopelessly insane, and in confinement at the McLean Asylum near Boston.” (Sen. Doc. Misc. #3, 32d Cong., 2d Sess.) Also an act was approved in 1854 as follows: “For the Purchase of the Copyright of a Work published by Thomas H. Sumner, wherein he describes his New Method of ascertaining a ship’s position at Sea.”
What He Did
Captain Sumner’s discovery of the Sumner Line or the correct concept of what the Line of Position means, is an excellent example of a discovery as opposed to an invention. He was placed in a position which indicated the principle of the Line of Position and he was shrewd enough to observe the meaning of it. There can be no better way of explaining the Sumner Line than to give Captain Sumner’s own account from his book on the occasion which resulted in the discovery.
Having sailed from Charleston, S. C. 25th November, 1837, bound to Greenock, a series of heavy gales from the Westward promised a quick passage; after passing the Azores, the wind prevailed from the Southward, with thick weather; after passing Longitude 21oW., no observation was had until near the Land; but soundings were had not far, as was supposed, from the edge of the Bank. The weather was now more boisterous, and very thick; and the wind still Southerly; arriving about midnight, 17th December, within 40 miles, by dead reckoning, of Tusker light; the wind hauled S.E., true, making the Irish coast a lee shore; the ship was then kept close to the wind, and several tacks were made to preserve her position as nearly as possible until daylight;
From "A New Method of Finding a Ship's Position at Sea," by Captain Thomas H. Sumner
when nothing being in sight, she was kept on E.N.E. under short sail, with heavy gales; at about 10 a.m. an altitude of the sun was observed, and the Chronometer time noted, but, having run so far without any observation, it was plain the Latitude by dead reckoning was liable to error, and could not be entirely relied on.
Using, however, this latitude, in finding the Longitude by Chronometer, it was found to put the ship IS' of Longitude, E. from her position by dead reckoning; which in Latitude 52oN. is 9 nautical miles; this seemed to agree tolerably well with the dead reckoning; but feeling doubtful of the Latitude, the observation was tried with a Latitude 10' further N., finding this placed the on her course, E.N.E., the ship E.N.E. 27 nautical miles, of the former position, it was tried again with a Latitude 20'N. of the dead reckoning; this also placed the ship still further E.N.E., and still 27 nautical miles further; these three positions were then seen to lie in the direction of Small’s light. It then at once appeared, that the observed altitude must have happened at all the three points, and at Small’s light, and at the ship, at the same instant of time; and it followed, that Small’s light must bear E.N.E., if the Chronometer was right. Having been convinced of this truth, the ship was kept on her course, E.N.E., the wind being still S.E., and in less than an hour, Small’s light was made bearing E.N.E. ½E., and close aboard.
The Latitude by dead reckoning, was erroneous 8 miles, and if the Longitude by Chronometer had been found by this Latitude, the ship’s position would have been erroneous 31 ½ minutes of Longitude, too far W., and 8 miles too far S. The ship had, from current, tide, or error of log, overrun her reckoning, 1 mile in 20.
Thus it is seen, that an observation taken at any hour of the day, and at any angle between the meridian and E. or W. points, is rendered practically useful, inasmuch as the Chronometer can be depended on.
It is almost unbelievable that before this no practical navigator had realized the full meaning of the Line of Position. By an interesting coincidence, Captain Sumner’s concept of the Line of Position is very close to the one held by the modern navigator, the essence of it being that the observer is on a circle of equal altitude
From “A New Method of Finding a Ship’s Position at Sea,” by Captain Thomas H. Sumner
with the geographical position of the observed body as the center. The Nautical Almanac is used to find this geographical Position of the body, that is, its Longitude Latitude, but called hour angle and declination. Figure 1 (reproduced from Plate III of Sumner’s book) will show Captain Sumner’s original illustration of the plot described in the quotation made above.
Captain Sumner’s considered concept of the circles of equal altitude is clearly illustrated in Plate I of his book, as is shown in Fig. 2 of this article. In Fig. 2, the geographical position of the sun is plotted, with circles of equal altitude plotted on the Mercator Projection, and a second series of altitudes are indicated after an elapsed time of nearly two hours. Sumner’s illustration would grace any modern text and is remarkably similar to the illustrations of the principles on which the Star Altitude Curves are constructed.
In teaching the principles of celestial navigation, the whole subject is greatly simplified if the student is directed to Plate I in Sumner’s book in which no mention is made of the celestial triangle. Instead the student’s attention is directed only to the geographical position of the observed body whose circles of equal altitude are at equal distance from the geographical position of the body. The longitude of the geographical position is the Greenwich hour angle as tabulated in the Nautical Almanac. The latitude of this position is the declination as tabulated in the Almanac, and the local hour angle is the difference of longitude between the meridian of the observer and the meridian through the geographical position of the body.
What Others Thought of Him
While it was obvious to the well informed that Sumner’s discovery was revolutionary, he still had to overcome the inborn conservatism of the nautical world in order to have his methods accepted. In an effort to sell his idea to the public, there appears under “recommendations” in Sumner’s book the following interesting testimonial:
In obedience to a resolution adopted at the last stated meeting of the “Naval Library and Institute,” in the following words, to wit: “Resolved, That A Committee of three members be appointed to investigate the New Method, of finding a Ship’s Position at Sea, by Capt. Sumner, and report at the next meeting.”
The Committee respectfully submit the following Report:
We have carefully examined the subject referred to, and find that Capt. Sumner’s method of ascertaining “The Bearings of the Land; of finding a Ship’s Position by projecting two of those Bearings, and of projecting the Sun’s true Azimuth, &c.” are all founded on spherical principles, as applied to Nautical Astronomy.
And your committee is of opinion, that in practice, Capt. Sumner’s discovery (for we can call it nothing less) will prove a useful auxiliary to the present knowledge of Navigators, and, as such, would recommend it to the attention of all persons interested in the promulgation and improvement of Nautical Science.
James Alden, Lt. U. S. Navy,
Sam’l R. Knox, Lt. U. S. Navy,
Geo. H. Preble, Passed Mid. U.S.N.
Naval Library and Institute,
Navy Yard, Boston, April 30th, 1843.
I certify the above to be a true Copy of the Report.
W. Wheland, Recording Secretary Navy Yard, Boston, 9th May, 1843.
It will perhaps surprise readers of the Naval Institute Proceedings to see that there existed a Naval Library and Institute as early as 1843.
In the Naval Academy Library is a copy of Sumner’s interesting book inscribed by the famous mathematician William Chauvenet and on the fly leaf of that is the following notation by Professor Chauvenet:
Sumner’s Method may be varied by computing the observations successively for two assumed Longitudes and determining two or four positions of the ship, according as one or two altitudes have been observed. This remark is due to a suggestion of Mr. Hilgard of the Coast Survey. July, 1850. W.C.
This and other comments by noted authorities show the importance of Sumner’s contribution to navigation. The quotation given, or an approximation of it, is given in Bowditch and also Lecky’s Wrinkles. Possibly the quotation was made from another edition of Sumner’s book, as they do not tally all the way through.
In the Nautical Magazine for 1844, Lieutenant H. Raper, Royal Navy, contributed an article headed, “On Captain Sumner’s Method of Determining the Position of A Ship.” In this article, Lieutenant Raper gives a great deal of credit to Captain Sumner and ends with the statement: “As a method of arriving out of the employment of the chronometer, it may be said briefly to enhance the utility of that instrument.” Lecky states that, “It must be clearly understood that the distinctive feature of Sumner’s process is that a single altitude taken at any time is made available for determining a line on the chart on some part of which line the ship is situated.” Lecky further states, “It will be observed that it did not then occur to Sumner to cross his Line of Position with the fixed one and so get a definite fix.” Lecky characterized Sumner’s Line as an astronomical cross bearing.”
Then, in typical Lecky style, under the caption “Honour Where Honour is Due” he writes:
This appears to have been the first recorded application of principles which have furnished the foundation of the system which Sumner worked out and published a half a dozen years later. In the first year of the publication of his book, an order was given to supply it to every ship in the United States Navy.
Then Lecky gets in a lick for himself:
The Bureau of Navigation at Washington adopted the same course with respect to Wrinkles ln Practical Navigation, an example followed later by our own Admiralty.
That very distinguished authority, Lord Kelvin, in alluding to Sumner’s method ‘Double Altitude” is credited with having said in the course of a lecture at Glasgow, that “It would be the greatest blessing to navigators, both young and old, if every other method of ordinary navigation could be swept away.”
While the acclaim of Sumner as the discoverer of the Line of Position is almost unanimous, a somewhat different slant is ^horded by the article on navigation in the British Encyclopedia. In that account is the following:
This method of finding both latitude and longitude at the same time is commonly known as “Sumner’s” method from the publicity given to it in 1847 by the publication of an excellent pamphlet on the subject by a master of that name in the American mercantile marine, although in a modified form it was practiced at a much earlier date in the British Navy under the name of “Cross Bearing of the Sun.”
However, when Sumner made his discovery, the method mentioned above was not in general practice, or at least Lecky, Lord Kelvin, and Lieutenant Raper of the Royal Navy made statements which seem to bear this out. It is probably a case similar to that of the credit due to Dr. Langley and the Wright brothers in the invention of the airplane.
The principle of Sumner’s method received a very important development when Marcq Saint-Hilaire proposed his method of comparing a computed altitude with the observed altitude of the observed body instead of the old time sight method. The Marcq Saint-Hilaire method, using the cosine haversine formula, has been used for many years as the standard method by many mariners.
Only within the past ten or fifteen years have simplified tables been published which compete seriously with the Saint- Hilaire method. Although Captain Sumner did not have these convenient tables, improved sextants, and chronometers checked daily by radio, it is obvious that his progressive and observing mind would have been the first to utilize these improved tools had they been available.
One assertion, lastly, seems to be not unsafe. In modern conditions of gunnery, the “useful defeat,” the defeat in which one sacrifices one’s self in order to inflict an equivalent injury on enemy, is a quasi-impossibility. We must, therefore, make the utmost use of our weapons and our means, cannonade and maneuver, to win the victory.—Baudry, Naval Battle.