618 



NAVY, UNITED STATES. 



capacity the projectile has, if instantaneously 

 stopped by some other body in any part of its 

 flight, to put that other body in motion. Con- 

 sequently, supposing a cannon ball in no de- 

 gree to penetrate armor plating against which 

 it is fired, but to be instantly and totally 

 arrested at the surface, this momentum is also 

 the measure of the shock or concussion the 

 ball will give to the armor. The ball, having 

 its motion extinguished, either the ship as a 

 whole or the part struck must be proportion- 

 ally moved ; and, remembering that the most 

 rigid sides of iron and wood will, still, bend, 

 and may fracture, while it is the nature of 

 inertia to prevent the communication of the 

 motion, instantaneously, to the whole ship, it 

 follows that the part struck, for a greater or 

 less area, and to a greater or less extent, ac- 

 cording to the conditions of the case, will move 

 from before the projectile which it arrests. 

 If this yielding be under a blow sufficiently 

 great, the effect will be permanently to bend the 

 plate, or to fracture it, perhaps to drive it into 

 the wood backing, and to start or crush the 

 latter. In this way the plates may be fractur- 

 ed, shattered or loosened, the bolts driven in, 

 or the structure of the ship, at the part, racked 

 or strained, and perhaps a leak produced. 

 Now, it is important to remember (a point too 

 often overlooked) that all these effects, per se, 

 are due to, and measured simply by, momen- 

 tum, and, hence, increased directly and simply 

 by increasing the product of weight and velo- 

 city (not of weight and the square of velocity). 

 Thus, if the two balls be of similar form, and 

 could act by momentum alone, then, at short 

 range, Sir Win. Armstrong's 110-pounder, fired 

 with 14 Ibs. of powder, and with an initial 

 velocity of 1,210 ft. per second, should have, 

 to the common 68-pounder, fired with 16 Ibs. 

 of powder, at an initial velocity of 1,580 ft. 

 per second, a damaging effect in the ratio of 

 110X1,210 to 68 X 1,580; or, nearly as 13 : 11. 

 But precisely to the extent that the material 

 and structure of the ship's side combine to 

 give rigidity and immobility to the part struck, 

 so that, while the gradual operation of inertia 

 will not allow the whole ship to recede, these 

 qualities refuse to allow the part to yield 

 through any considerable extent so as to be 

 crushed in or fractured and recoil, it will then 

 be true that one or both of two other results 

 must follow, namely : the projectile must ex- 

 pend the quantity of force stored up in it in the 

 way of compressing, flattening, or crushing its 

 own mass, in the first case, perhaps rebounding, 

 either whole or fractured, or else it must ex- 

 pend the same force in the way of overcoming 

 the cohesion and resistance of the materials it 

 strikes, and pushing or cutting its way into or 

 through them. But this quantity of force or 

 work stored in the moving ball is proportion- 

 al to the product of its weight into the square 

 of its velocity ; that is, the icorlc varies as W X 

 V 2 . It is already evident, then, that the exe- 

 cution of a ball or shell in the way of punch- 



ing or penetrating the armor, and generally 

 the sides, of a ship, must also be in this ratio : 

 it increases, so far as the mere force is con- 

 cerned, as weight and square of velocity. 

 Supposing, then, their entire energy to be ex- 

 pended in the way of penetration, the projec- 

 tiles above named would be capable of damag- 

 ing effect in the ratio of 110 X 1,210 2 to 68 X 

 1,580* ; or, nearly as 16 : 17 ; so that here, allow- 

 ing for the Armstrong projectile the highest 

 initial velocity claimed for it, the advantage is 

 still on the side of the 68-pounder, with larger 

 firing charge and higher velocity. The weights 

 of projectiles of like form being, in general, as 

 the products of their diameters and densities, 

 it may be correctly said, also, that their punch- 

 ing or penetrative capacity will be as the prod- 

 ucts of the three factors, diameter, density, 

 and velocity square. 



Thus, projectiles can have two sorts of effect 

 upon obstacles, say the armor or sides of a 

 ship, namely, that of pushing or crushing away 

 the part before them until their motion is con- 

 sumed in imparting an equal motion ; or, that of 

 overcoming their own cohesion or that of the 

 part struck ; in the latter case driving or cut- 

 ting into the part until the work stored up in 

 them is in this way expended. But since, 

 generally, under the instantaneous blow of a 

 projectile the armor and side of the ship, in 

 degree, both yield and refuse to yield, it fol- 

 lows that, in actual cases, the two kinds of 

 effect will usually be mixed, though one or the 

 other may predominate. It would appear, 

 however, to follow that, other things equal, 

 very large and heavy projectiles, thrown at a 

 lower velocity, should be relatively more ef- 

 fective in the way of fracturing or shattering 

 armor, and straining the general structure of 

 the part, while shot or shell of less weight, 

 from guns bearing a heavy charge of powder, 

 and giving a high initial velocity, should be 

 more effective in the way of penetrating the 

 armor and sides, as where the object may be 

 to cause a leak or to carry shells into the inte- 

 rior. This distinction, questioned by some 

 authorities, and not always clearly drawn, 

 appears, still, to be that more generally held 

 as practically correct. 



Sir Wm. Armstrong concludes that it is not 

 by piercing small clean-cut holes with steel shot, 

 that a ship is to be disabled or destroyed, but 

 by knocking large ragged holes in the side, and 

 rendering the interior untenable from splinters. 

 Stating the case, however, in the most general 

 way, it appears that the greatest amount of de- 

 structive effect will be produced by the guns 

 which can give to the heaviest projectiles the 

 greatest velocity ; and this amounts to saying, 

 in other words, those which with a given cal- 

 iber and weight of projectile admit of being 

 fired with the heaviest charge of powder. In 

 spite of some assertions to the contrary, the 

 opinion is now gaining ground that the superior 

 execution of the new wrought-iron, hooped, or 

 otherwise strengthened forms of ordnance, over 



