DEVELOPMENT OF ORDNANCE AND ARMOR IN THE IMMEDIATE PAST AND FUTURE[*]
The object of my paper to-day is to bring to your attention and to discuss recent developments in ordnance and armor, and to point out the direction of probable further advances. Enormous strides have been taken by both the offense and the defense in naval warfare since the days of smoothbores and wooden walls, but there is room for further progress, and although this will probably consist almost entirely in the perfecting of details, yet to the navy most successful in doing this may come the reward of a decisive superiority.
It is an axiom that the success or failure of any mechanical device, complex or simple, lies in greater or less perfection of details, and this is perhaps truer of ordnance than of anything else. The best guns and mounts are useless if the primers or sights are defective; the best projectiles are of little value if their fuses fail. Of course the prime factors for success are skill and zeal on the part of those who handle the guns, but these qualities granted, then the difference between perfection and inefficiency lies in the working out of details.
Let us commence then with the gun and consider what is being done to increase its efficiency and what more can be done. The desirable qualities in a gun are safety, power, accuracy, rapidity of fire, and cheapness. Safety and cheapness depend upon material and method of construction; power depends upon size of chamber, caliber, and length of bore; rapidity of fire depends principally upon the system of breech closure; accuracy depends, as far as the gun itself is concerned, on workmanship.
Forged steel as a material and the built-up methods of construction are now in almost universal use, and the records of proving ground and service firings show that they furnish an ample margin of safety. Wire-wound guns are coming somewhat into use, but their superiority over built-up guns, either as regards safety or cheapness, is trifling or non-existent. I suppose no experienced person doubts that an efficient, safe and cheap gun can be made of cast steel or can be forged in one piece, but the manufacture of such guns can only be defended on the score of cheapness and rapidity of production, and they cannot be regarded as in any sense equal to guns built on the present system. It would appear, therefore, that there has been no important progress made in the art of gun-building in the recent past, nor is there likely to be any in the immediate future, and I think we need have no fear of our present guns becoming obsolete before they are worn out.
The power of any gun depends on its caliber, length, and the size of its powder chamber. Taking a gun of any given caliber, we can increase its power almost indefinitely by increasing the size of its powder chamber so that it will contain more and more powder, and at the same time increasing its length of bore so that the powder may have time to burn; but this method is so expensive, both as regards weight and money cost, besides involving increased difficulties in handling and supplying ammunition, that development along its lines ceased some years ago.
Universal practice has fixed the size of the powder chamber of modern guns at a point which permits the use of a brown powder charge of about half the weight of the projectile, which itself weighs in pounds about half the cube of the caliber in inches, and the serious disadvantages which would attend any very marked departure from this practice render a radical change improbable. The plan of increasing power by lengthening the bore, however, has of late been followed to an extent which seems to me to be unwise; based, as it appears to be, on mistaken notions as to the action of the new powders, whose introduction has been followed by the manufacture of guns of sixty and even eighty-caliber length. With the old brown powder an increase of length of bore from 40 to 50 calibers adds but about 100 f.s. to the muzzle velocity of a large gun, and less than that to the muzzle velocity of a small gun; and with the new smokeless powders, for reasons which I shall point out later on, the gain from increase of length is even less. To compensate for this slight gain in velocity we have increased weight, cost and difficulty of manufacture, with decreased mobility. I think it quite certain that an increase of length of bore beyond 35 or 40 calibers is inexpedient and that there will be no marked future progress in this direction.
The true method of increasing power is by an increase of caliber, and the most important question in regard to the gun is whether we have reached the proper limit to development in this direction, or whether we shall find it desirable in the future to build larger guns than we now have in use or contemplation. Of late years the tendency has been the other way. Krupp and Armstrong no longer find purchasers for their 100 and 120-ton guns, and none of England's latest battle-ships carry the 16 ¼-inch gun. This retrograde movement was due to the fact that the power of the gun so exceeded that of armor as to render it advantageous to sacrifice the unnecessary excess for gains in other directions. The advent of hard-faced armor has put a stop to this movement, and the question now is, will future developments result in either a future decrease of caliber or a return to the largest calibers yet made and even an advance beyond them? There is no question as to the great advantages of large caliber; the larger the gun the more destructive in increasing ratio is its fire, but the sacrifices attending the use of very large guns lead us to restrict their use as much as the necessities of the case admit. If the 13-inch guns will suffice to do any work which they can be called upon to do, then we are not likely to build larger guns on the ground that the latter will do the work more easily. We must, however, have on our battle-ships guns capable of overcoming any defense which an opposing battle-ship may present to them. The question then is, are future armor developments likely to result in a protection to ships which the 13-inch guns cannot overmatch? No armor plate has ever yet been made which a good 13-inch projectile, at moderate range and with normal impact, would not perforate, and I incline to the opinion that there never will be. The power of the 13-inch gun is now limited by the strength of its projectile, which, unless of the most superior quality, smashes on hard-faced armor, and it is more than likely that future advances in armor manufacture will be accompanied or preceded by equal or greater improvements in projectiles. I conclude, therefore, that an increase of power beyond that of the 13-inch gun will not become necessary, and consequently that no larger calibers will be adopted. As far as reduction in caliber is concerned, this would be clearly unwise at present, and even if, in the future, the 12-inch or a smaller gun develops sufficient power to overcome any armor, it is doubtful if the gain of weight due to the change will be of sufficient importance to justify it. There is no reason why the rate of fire of a 13-inch gun should not be practically the same as that of a 12-inch gun; its destructive effect is much greater; and, in my judgment, having adopted the 13-inch caliber for our battle-ships, we should, and will, continue its use in the future.
The most striking advance in ordnance in recent years has been the application of the rapid-fire principle to large guns, and it is very important to decide how far this development can be carried. We hear of 8-inch, and even lo-inch, rapid-fire guns, but the term should properly be applied only to guns using metallic cartridge cases. With such guns a quick-acting breech mechanism can be used, and the time required to prime the ordinary type guns is saved. Moreover, with calibers small enough to allow the use of fixed ammunition there is a considerable saving of time, from there being required but one motion in loading instead of two. Thus it is that the modern R.F. gun of 5-inch caliber or less can be fired in practice and without aim at the rate of 10 or 12 shots a minute; or, allowing about ten seconds for aiming, we may say that the service rate of fire of the 5-inch R.F. gun should be from 3 to 4 rounds a minute. When we go to the 6-inch caliber, where the weight of fixed ammunition would require two men to handle it, the advantage of single loading is lost, but still the saving of time from the use of the primed cartridge case is considerable, and with a well-drilled crew the service rate of fire of the 6-inch R.F. gun should be from 2 to 3 rounds a minute. The 6-inch R.F. gun is in general use already, and its great advantages over the ordinary type gun of equal caliber are now universally admitted. Can we hope to extend the R.F. system still further, or has the limit of progress in this direction been reached?
The interval between rounds with any gun is made up of (1) the time to open breech, (2) the time occupied in cleaning-gun or mechanism, (3) the time to load projectile, (4) the time to load charge, (5) the time to close breech, (6) the time to prime, if) the time to point and fire. Considering the 8-inch caliber, let us see how these times can be reduced to a minimum and to what limit they tend. With our present breech mechanism the operations of opening and closing the breech occupy 4 ½ seconds each. The automatic opening of the breech during counter-recoil, which is now being used on heavy guns abroad, will save 4 ½ seconds time. The adoption of a mechanism actuated by a single motion, such as used on the regular R.F. guns, would have perhaps 7 seconds, 3 ½ in opening and 3 ½ in closing, but would necessitate the use of a metallic cartridge case which, as will be seen further on, has more than compensating disadvantages. Sponging or in any way cleaning out bore or chamber is an entirely unnecessary waste of time, and the only thing which should be done after each fire is to wash off the gas check with a marine sponge, which can be done while the gun is being loaded. The gun should also be primed while being loaded. The use of a primed cartridge case would, therefore, not save any lime as far as these operations are concerned, neither would the use of a cartridge case save any time in loading; fixed ammunition is entirely impracticable for so large a gun as the 8-inch, so that double loading is a necessity. The use of a metallic cartridge case certainly would not make the operation of loading any more rapid, adding, as it would, some 50 pounds to the weight of the ammunition and requiring extraction and removal after each round, while at the best only saving some seven seconds on time of opening and closing breech.
The time taken to load shot and charge and to point and fire depends upon the efficiency of the ammunition, handling and gun-pointing apparatus, and upon the skill of the gun's crew, but the latter is by far the most important factor. As an illustration of this it may be said that the firing interval of our 8-inch turret guns at target practice ranges from 2 minutes to 8 or 9 minutes on different ships having the same mechanical arrangements, and, be it remarked, with far greater accuracy of fire on the ship with the smaller interval.
We must conclude, then, that with the 8-inch caliber, and a fortiori with larger calibers, no material increase in rate of fire can be attained by mechanical improvements in the guns themselves or by the use of the rapid-fire principle. The real progress in this direction in the future will be the result of constant and zealous exercise far more than of mechanical improvements.
When you read that the Elswick R.F. 8-inch gun has been fired, on shipboard, 3 rounds in 30 seconds, beginning loaded, you must not conclude that the Elswick 8-inch gun is superior to our own, for this is not the case. The true explanation is that the men who did the firing were well drilled and working for a record under intelligent supervision, and with equal zeal and an equal amount of practice our 8-inch gun's crews would do as well.
When we leave the 8-ineh caliber another condition arises, i.e., the weight of the projectile becomes too great for convenient hand loading. With 8-inch guns the projectiles should be kept about the gun, in racks or otherwise, and loaded entirely by hand. With the larger calibers the shell must be hoisted from below, together with the powder charge, and loaded by mechanical means, and the rate of fire depends almost entirely upon the efficiency of the ammunition-hoist and the skill of the men handling it. A small saving of time can be effected by automatic opening of the breech during counter recoil, but this amounts to about 15 seconds at the most; and the gain which will result from acquired skill in loading and pointing is far more important. No attempt should be made to clean bore or chamber. There is no danger of burning material being left in the chambers of the long guns now in use, and the difficulty of sticking of the shot in loading can be overcome by the use of a loading shoe which lifts the axis of the projectile to the same level as that of the bore. A well-drilled crew should be able to fire the lo-inch gun at the, rate of one aimed round every two minutes, and the 12 or 13-inch guns every three minutes or less. The greater rapidity of fire of the lo-inch caliber is largely due to the fact that the half-sections of the powder charge are not too heavy to be removed from the hoist by hand and inserted in the powder chamber while the hoist is being lowered for another round. With the 12-inch and 13-inch this method, though perhaps practicable, has not been tried, and consequently the estimate is made on the supposition that the hoist has to be stopped in three successive positions while the shot and the half-charges are successively rammed home.
To sum up, it may be said that rapidity of fire with heavy guns depends far more upon the skill to be acquired by constant practice than it does upon further perfection of mechanical details. No man can properly control the ammunition-hoists and the elevating and training gear of a heavy turret gun unless he has learned to do it by constant exercise, and when we consider that the victory or defeat of a battle-ship will depend almost entirely upon the greater or less skill with which her turret guns are handled, surely there should be no lack of such exercise. Daily drill in handling all the mechanical appliances, and especially in pointing the guns at moving objects, should be absolutely insisted upon on every ship in our Navy, and the larger the guns the more necessary this daily drill is.
The next point to be considered is the possible increase of efficiency of gun mountings.
One considerable improvement has just been made in the carriages for broadside guns, namely, the adoption of what is known as a pedestal mounting, which enables the usual arc of train to be attained with a smaller port opening than with former mounts, and, what is of great importance, without the use of sponsons.
The most important change, however, is the extension of hand-working to the largest guns. The 12-inch guns of the Iowa will have hand-worked mounts, and so probably will the 13-inch guns of the new battle-ships, and it is well to consider how this is accomplished and just what the advantages and disadvantages of the system are.
In the first place it must be borne in mind that hand training is and always will be impracticable for heavy guns in thick-armored turrets. The Indiana's 13-inch turrets, for example, can be trained at a speed of 10° a minute by eight men when the ship is on an even keel, but the least heel will render it impossible to move the turret from the position of train on the lee beam. In future designs the turrets will be so nearly balanced as to train with about equal ease on an inclined or a level deck, but the slowness of the movement and the speedy exhaustion of the men on the cranks must always operate as a bar to the use of hand training, except in an emergency when the usual training machinery has been injured.
In the same manner, though not quite so decidedly, we are prevented from using hand power for hoisting ammunition and for loading. Rapidity of fire is too important to be sacrificed to the extent which would necessarily be the case should power hoists and rammers be dispensed with.
The elevating and depressing of heavy guns by hand has been rendered practicable by pivoting the gun slide at the center of gravity and mounting it on knife edges to reduce the friction. In this manner we make it possible for two men to move a 12-inch or 13-inch gun and slide up or down with sufficient rapidity for all practical purposes. Lastly, the return of the heavy gun to battery is now accomplished by springs, as in the case of small guns, and thus the use of hydraulic or other power brought up by pipes or wires from below is no longer necessary.
To sum up, then, the advantages of so-called hand working of heavy guns are: 1st. That in the complete absence of all other power, caused by breaking of pipes, wires or motors, the operations of running out, hoisting ammunition, loading, training and elevating the guns can still be performed by hand, though the hoisting of ammunition and the training will be but slowly and laboriously accomplished. 2d. That there are many less pipes or wires and motors, with consequent less chance of disablement in action. With the old arrangements, not only would an injury to the power system anywhere absolutely prevent any further use of the guns, it being impossible to either run them out or to elevate them without power, but the numerous connections to the recoil cylinder and elevating ram greatly increased the chances of injury to some part of the power system.
The disadvantages of the hand-worked mounts are, 1st, the necessary increase of time required for all movements which are performed by hand, and 2d, the increase in size of port opening caused by the necessity of pivoting the system at its center of gravity.
It will be seen, therefore, that while hand-worked mounts for heavy guns have sufficient advantage to probably cause their increased use, yet their adoption is not a radical advance, and no great gain can result from their furthest possible development.
The next question to consider is to what extent powder and projectiles can be further improved.
The introduction of so-called smokeless powders into general use is now an assured though not a completed fact. Its results will be far-reaching and will enormously increase the efficiency of ordnance.
All the smokeless powders in present use are colloids, either of gun-cotton, of nitro-glycerine, or of a mixture of the two. Nitro-glycerine and gun-cotton are the two most powerful explosives known; in other words, the potential energy of a given weight of these two substances is greater than that of the same weight of any other chemical compound of sufficient stability for practical use. If this potential energy be instantaneously converted into energy of motion, as when gun-cotton or nitro-glycerine is detonated, the resulting force is too great to be controlled, but by changing the physical state of the explosive —making it a colloid—we can cause it to burn progressively instead of detonating, and thus we can control its energy. In accomplishing this result, however, we have reached a limit only to be passed by the discovery of an entirely new order of explosives, such as is unknown to our chemistry. We have trained to our service the most powerful forces known, and further possibilities of advance are not apparent. To increase velocities beyond what they now commonly are with smokeless powders, namely, 2400 to 2600 foot-seconds, we must increase the weights of our powder charges and the lengths of our guns, and accept the attendant disadvantages. The gain from increased length of bore alone is small; that from increased capacity of chamber and increased length of bore is as great as you please, but is accompanied by many inconveniences and difficulties, while the gain from increased weight of charge alone is attained only at the cost of increased powder pressures with attendant erosion of bore and shortened life-time of gun. If we allow 20 tons per square inch maximum pressure, we can perhaps get 2800 foot-seconds instead of 2500 or 2600 with 15 to 16 tons, but the life-time of our guns will be greatly lessened by the change.
Assuming that we are unwilling to allow much higher pressures than at present, we have the following advantages from the use of smokeless powder:
(1) An increase in velocity of about 500 foot-seconds with consequent flatter trajectories and greater penetrating power.
(2) Absence of smoke, increasing the facility of maneuvering of the fleet, as well as that of aiming the gun.
(3) Reduced weight of powder charge, as well as absence of residue, facilitating loading.
While there is but one disadvantage—increased cost.
With the adoption of a reliable smokeless powder for service use in all guns, then, we appear to have come near to the probable limit to the power of the gun, as well as near to the probable limit to rapidity of fire.
But have we yet reached the point where it can be said that we have a reliable smokeless powder? Evidently we have not such a powder in service use, and the most that can be said is that the goal is in sight.
The fact is that almost all the known varieties of smokeless powder are unreliable, deteriorating after a time and gradually decomposing, and it is the fear of the results of such decomposition, when large quantities of the powder are contained in closed tanks or cartridge cases, which has operated to prevent their general service use.
It is probable that the French, who were the first to develop a smokeless powder, are to-day the only nation having a perfectly reliable one. They have in service use in all their guns a pure gun-cotton colloid, and we are endeavoring to follow in their traces.
The English cordite, which contains 58 per cent, of nitroglycerine, is commonly reported to be unreliable, though they have had sufficient confidence in it to issue it to the service.
The reason why we prefer to follow the French example is that we consider any powder containing nitro-glycerine unsafe. It is thought that in such a powder as cordite the nitro-glycerine is held in the colloid of gun-cotton as water is held in a sponge, and that pressure will cause the nitro-glycerine to exude, in which case even a slight shock will produce detonation. Moreover, it is thought to be impossible to make a really stable combination of heterogeneous nitro-substitution products; the interaction of the nitro-glycerine and gun-cotton and of the impurities in each will result, especially at high temperatures, in a slow decomposition and increasing instability. Gun-cotton, on the other hand, we know from many years of experience to remain unchanged through long periods of exposure to varying temperatures, provided it be kept wet. Now the form of a guncotton colloid protects its substance from the air much as water protects wet gun-cotton, and consequently there is every reason to suppose that it will remain unchanged if properly made. Again, the temperature of combustion of nitro-glycerine is much higher than that of gun-cotton (3469° C. to 2710° C), and this results in greatly increased erosion of the bore when nitroglycerine powders are used.
With regard to the common notion that with smokeless powders great length of bore is desirable—this is certainly not the case with gun-cotton powders; 50 pounds of gun-cotton will do about the same work as 100 pounds of powder, and its combustion will develop about one and one-half times the volume of gas at about the same temperature. Consequently, if used in the same gun in this proportion, the gun-cotton will evidently produce a much higher maximum pressure if it burns as rapidly as the powder, or, if made to burn more slowly, it will produce a much more sustained pressure. But when all the charge is consumed the pressure of the gun-cotton gases will fall off much more rapidly than will that of the powder gases, because out of the 100 pounds of powder are formed 56 pounds of solid or liquid residue, from which the 44 pounds of expanding gases extract heat which keeps up their pressure, while the 50 pounds of gas from the gun-cotton has no reserve heat to draw upon. In other words, with a gun-cotton powder the maximum pressure is carried further along the bore than with an ordinary powder, but when the gas ceases to be evolved the pressure falls more rapidly, and at the muzzle of a 40-caliber gun the pressure is less with the former than with the latter.
Turning our attention next to the projectile, let us regard this as the vehicle for the energy of the gun. By the use of smokeless powders we have greatly increased the amount of energy which the projectile conveys, and by the use of Harveyized armor we have greatly increased the amount of energy required to overcome resistance to perforation. The next step, and a most important one, is to so improve the projectile that it shall be able to deliver the whole energy of the gun in the form of work done on the armor plate. Neglecting the work lost in overcoming the resistance of the air in flight, the projectile of course delivers the whole energy of the gun at the point of impact, but the manner of distribution of that energy is all-important. If the projectile is strong enough to bear the impact unbroken and undistorted, then all its energy is usefully employed in perforating or cracking the plate; but just to the extent that it breaks or is distorted, its energy is dissipated in useless work upon itself. Now the A.P. projectile within a few years had been developed to a point such that it was capable of withstanding the strains of impact against steel armor without injury to itself, and consequently it performed its function of a vehicle of energy perfectly, delivering the whole energy of the gun in the form of useful work on the plate. The successful introduction of the process of surface-hardening steel armor plates changed this completely. The projectile was no longer capable of withstanding the strains of impact against the hard-faced armor—it broke into fragments, and a very large percentage of its energy disappeared in useless work upon itself. In overcoming this defect a long step in advance will be taken, and in this direction real progress can still be made.
I hope within a short time to see the A.P. projectile again developed to a point close to that perfection which would consist in the delivery of the entire energy of the gun in the form of work on the plate, and when this happens I estimate that the value of our present armor will have been diminished about 20 per cent.
As far as common shell are concerned, in our own service we are abandoning the use of cast-iron and cast-steel shell, and propose to use only forged steel shell, the distinction between the armor-piercing and common shell consisting only in the fact that the latter has thinner walls than the former, with the resulting advantage of a much larger bursting charge and the compensating disadvantage that it will pierce less armor. It is a question whether it will not be advantageous to use armor-piercing shell only for guns of large caliber, 8-inch and above, and to use common shell only for the rapid-fire guns. With present practice it will be somewhat difficult to decide, in action, what sort of projectiles it is best to use.
Shrapnel, the third kind of projectile in use in the Navy, have a very limited use. They could be used effectively against exposed men in boats or on shore—also against torpedo-boats—but their efficiency depends entirely upon accurate time explosion, and that, under service conditions, is out of the question. I believe that the use of canister from the rapid-fire guns would serve a far better purpose than that of shrapnel under almost all circumstances, and I think that their issue in small numbers is very desirable.
None of the improvements in projectiles referred to are of a radical nature, but there is one direction in which popular opinion believes an advance amounting to a revolution will some day be made. Many people think that the use of high explosive shell will revolutionize naval warfare, and that the adoption of such shell for service use only awaits the appearance of the great American inventor who will reveal the secret of how to use them safely. There is so much misconception on this subject that it seems worth while to consider it at some length. The danger in firing any explosive from a gun lies, of course, in the possibility of its going off in the gun and bursting the latter, and the greater the quantity of the explosive the more likely is it to go off and the more serious will be the effects of such an accident.
Whatever be the character of the gun, the explosive must be contained in some sort of a projectile, and that projectile must be given velocity by some sort of an accelerating force, be it the expansive force of compressed air or of powder gases, and the acceleration of the projectile at each instant must be a true measure of the force acting upon the projectile and upon the explosive contained in it. When the driving pressure on the base of the projectile is greatest, then is the acceleration of the projectile greatest, and then is the shock tending to explode it greatest. Nothing is gained by applying a small pressure at first and gradually increasing it; the maximum pressure on the base of the projectile, whether it occur before the projectile has had time to move or just as it reaches the muzzle of the gun, is what measures the danger of an explosion. Consequently, whatever form of gun is used for faring high explosive shell, the one requirement for safety is that the maximum pressure on the base of the projectile shall not be too great. It is just as safe to fire any high explosive shell from a powder gun as from an air gun, provided we limit the powder pressure to the pressure used in the air gun. This being understood, we have to consider the fact that the liability to explosion depends both upon the amount of explosive and upon its character. The column of explosive contained in the shell being driven forward with accelerated velocity, the greater the height of that column the greater the pressure upon its base, and if that pressure reaches a certain point an explosion will result. This is the reason why experiments with shell containing small amounts of high explosive have no value. Because a pound of nitro-glycerine can be fired with high velocity from a gun, it by no means follows that 100 pounds can. The sensitiveness of nitroglycerine to shock will prevent our ever using that on board ship, and although some other explosive compounds are slightly more powerful that gun-cotton, the safety of the latter, and our long experience with it, render it unlikely that we will adopt any other high explosive for service use. Now in the manufacture of gun-cotton we habitually apply a pressure of about three tons per square inch to the wet blocks, and we know this to be a safe pressure; consequently there is no danger in firing shell loaded with wet gun-cotton from powder guns provided we keep within this limit. This will allow us to safely fire about 175 pounds of wet gun-cotton in a 12-inch shell weighing 800 pounds at about 1600 foot-seconds muzzle velocity with our present 12-inch gun and powder. Such a shell, however, must necessarily have very thin walls, and there is no chance of its penetrating through even thin plates without breaking up. The wished-for destructive effect must be obtained, if at all, from detonation on impact. With a thick-walled shell containing only a small quantity of high explosive, it might be possible to delay detonation until the projectile had entered the ship, but the destructive effect of such a shell is no greater than that of a similar shell burst by gunpowder. In other words, the only possibility with the high explosive shell is to us as great a weight of explosive as can be safely thrown, and to provide means for its detonation on impact, and to trust to the effects of such a detonation outside the ship. How destructive these effects would be we do not know, but for my own part I believe they are greatly overestimated.
As to the means for detonating the shell on impact, this is really the most serious problem to be worked out. No high explosive can be really detonated without the use of fulminate of mercury, and this is far more sensitive to shock than the main charge of the shell. Consequently, the real danger lies in firing the detonator, not in firing the main charge of explosive. With wet gun-cotton, moreover, a dry gun-cotton primer is needed as well as fulminate. However, this problem has been solved, and as a result of actual tests, I feel confident that we can at any moment put on our ships shell carrying over 20 per cent, of their weight of gun-cotton and capable of being safely fired at 1600 foot-seconds velocity and detonated on impact. There is absolutely nothing in the idea of special guns, air or other, being required for this; neither are any special forms of shell, cushioning devices and such, desirable or useful. The ordinary guns, with shell of ordinary form—only thin-walled so as to carry a large charge—and the ordinary powder charge, only reduced in weight, are all that we need or are likely to ever use, and, in my judgment, we could safely begin their use to-day if it were thought desirable to do so. But here is the rub. No one has entire confidence in the safety of such shell. The very idea that hundreds of shell, each charged with two hundred pounds of gun-cotton, are stored away in the magazines and must be brought up from below, loaded and fired in the heat of action, brings before the imagination such horrid pictures of the disastrous results of an accidental explosion in the gun, or anywhere inside the ship, that the mind refuses to be quieted by ex cathedra assurances that there is no danger. I have been present at numerous firing trials of high explosive shell, and I have been greatly impressed by the evident state of strain of the spectators, most of whom have been persons of long experience on the firing ground. These were all shell of comparatively small caliber, and I am convinced that the service use of large high explosive shell would produce a demoralizing effect upon both officers and men which would more than outweigh the possible increased destructive effect of such shell. Of course, this feeling of distrust would in time disappear if no accident occurred, and I only mention it as being a more potent reason for not putting high explosive shell on shipboard than is any difficulty in their actual manufacture and use.
As a natural sequence to the foregoing discussion of projectiles we now come to that of armor. In a paper which I had the honor to read here last year I argued for the continued use of armor, and pointed out its enormous advantages necessarily resulting from the fact that it effectually prevented the entrance into a ship of large capacity shell and of the multitude of projectiles delivered by the small rapid-fire guns. The first of these advantages is greatly reduced by the fact that the so-called armor-piercing shell are capable of being made truly so by the use of proper bursting charges; but even so, consider how much is gained if our armor will keep out all projectiles not of a caliber exceeding its thickness.
Very few large guns can be carried by even the largest ship, and their rate of fire is slow. It is well worth while to pay the price for immunity from damage by the great number of small shell, even though we cannot escape the possibility of having our armor pierced by an occasional shell of large caliber.
Since the manufacture of armor was revolutionized by the discovery that face-hardening heavy steel plates was practicable, some further advance has been made by improvements in the methods of manufacture. It is found that a secondary forging of the plate, after carbonizing its face, but before tempering it, improves its resistance both to cracking and to perforation, and I think it can safely be said that we are now making the best armor in the world. Certainly all the tests abroad of which I have knowledge indicate the superiority of American to foreign made armor plate. Our nickel steel, carbonized, Harveyized, reforged plates are to-day equal in resistance to all steel plates, as made a few years ago, 60 per cent, thicker. That is, at present an 8-inch plate, when attacked by an 8-inch projectile of the best quality, requires for perforation a striking velocity of about 1900 foot-seconds, whereas the same projectile, with equal velocity, would have perforated a 13-inch steel plate. Last year I was of opinion that after our projectiles had been perfected this difference would nearly, if not quite, disappear, but further experience has convinced me to the contrary, and I now think that we cannot hope to reduce the lead of the face-hardened plate more than about 20 per cent., which would leave it finally about 30 per cent, better than the simple steel plate. This of course is a very great advance, and while partly due to other improvements, it is not at all an exaggeration to say that the successful introduction of the Harvey process has revolutionized armor manufacture.
With the best projectiles which we have to-day fired with the velocities given by smokeless powder, and striking normally at 2000 yards range, I estimate that complete protection will be given by our present armor plate if of the following thicknesses:
Against the 4-inch gun, 4-inch armor,
Against the 5-inch gun, 5-inch armor,
Against the 6-inch gun, 7-inch armor,
Against the 8-inch gun, 10-inch armor,
Against the 10-inch gun, 14-inch armor,
Against the 12-inch gun, 17-inch armor.
Of course the chance of normal impact is very small, and it may fairly be said that armor one caliber thick, under service conditions, will give complete protection from any gun below the 10-inch, 12-inch armor from the lo-inch gun, and 15-inch armor from the 12-inch gun. As for the 13-inch gun, we must trust principally to the small chance of being hit for protection against its projectiles.
It may be interesting to hear a word about the capped projectiles which have given remarkable results in recent tests. It has been proven by numerous trials of shell with and without caps, that their use tends to prevent the projectile from being broken up on hard-faced armor, and consequently greatly increases its perforating power. This appears to be because the cap, made of very soft metal, not only supports the point, but also acts as a lubricant for it. Once through the hard surface and the rest of the plate is comparatively easy to penetrate. We are in hopes, however, to learn before long how to make projectiles which will do the same work without caps as present ones do with them, and as I have said before, this will be a most important step in advance.
As to the distribution of armor on our ships, we have made some recent improvements, such as raising the belt armor slightly and adopting elliptical balanced turrets. I think, however, we need to go further in the first direction, and as far as turrets are concerned, we need above all to increase their floor space. One of the greatest bars to rapid working of the turret guns of most of the ships we now have is the cramped space in which the guns' crews have to work.
I have reserved for my continuing paper to-morrow the important subject of the steps which have been, and still need to be, taken to improve the accuracy of gun fire, and now, in conclusion, I want to say that I hope you will not understand me to claim that our ordnance material is perfect, or even that it is not in many ways actually defective. What I do claim is that no part of it is so defective as to be incapable of a high state of efficiency in the hands of zealous and intelligent men; that what it chiefly lacks is in small details, which can and should be improved on board each ship, and that the skill born of frequent practice will bring it nearer to perfection than any probable improvements which can be made by its designers.
[*] The first of two lectures delivered before the Naval War College, Newport, R. I., in the summer of 1896.