422 REPORT— 1866. 



whether this vis viva be the result of a heavy shot and a low velocity, or a light 

 shot and a high velocity. Thus the 10'5-ineh gun with a spherical steel shot 

 of 165 lbs., and a charge of 35 lbs., gives a striking-velocity at 200 yards of 

 1470 feet, and a " work " on impact at 200 yards of 2472 foot-tons *. 



If the same gun be fired with an elongated steel shot of 300 lbs. and charge 

 of 35 lbs., the " work " will be practically the same at 200 yards, viz. 2472 

 foot-tons. 



The effect of these two projectiles may therefore be assumed to be equal ; 

 that is, either of them would punch the same hole. 



This, however, is only true in the case of projectiles of the same diameter ; it 

 would not hold good if the comparison had been made between a shot of 10-5 

 inches diameter, and a shot of 9-22 inches diameter. It is also necessary that the 

 shape of the head, or front part of the shot, should be the same in both cases. 

 Thus, when a comparison is made between a spherical and a cylindrical shot, 

 the head of the latter should be hemispherical. If the cylindrical head be 

 pointed or elliptical, it will have a certain advantage over the spherical form. 

 In the experiments with steel projectiles which have taken place in this 

 country up to the present time, the form of the head has been, generally 

 speaking, hemispherical ; the effects there are fairly comparable. 



It has been said that the diameters of the shot should be the same, in order 

 to ensure a dii'ect comparison. Recent experiments, however, have shown f 

 that with projectiles of different diameters the vis viva, should vary as the 

 diameter nearhj. That is to say, the force required to punch a 10-5-inch hole 

 is to the force requii-ed to punch a 9'22-inch hole as 10-5 is to 9*22 nearhj ; 

 so that, if it be found that 2472 foot-tons are required to send a 10-5-inch 

 projectile through the side of an iron-clad, the same effect, as regards pene- 

 tration, wlU be produced by 2171 foot-tons in the case of a 9-22-inch pro- 

 jectile. 



Let us now examine some of the principal experiments which have taken 

 place in this country in relation to iron-clad sea defences J. 



In the remarks on these striictures and the effects observed, the following 

 points will be chiefly attended to, viz. : — 



1st. Experiments against targets which represent actual sea-going vessels. 



2nd. The effects produced by guns of those calibres only which are likely 

 to be carried on board ship. 



3rd. In most cases, solid steel shot. 



The accompanying brief description of the several targets alluded to in tlie 

 Tables is inserted here for reference. 



Warrior.- — This target represented a portion amidships of the frigate of that 

 name. It is a specimen of an iron armour-plated ship. 



* The vis viva of a body in motion is the whole mechanical cfTcet which it will prodnco 

 in being brought to a state of rest, without regard to the time occupied ; and it varies as 

 the weight of the body multiplied by the square of its velocity. 



Tills mechanical effect, or " work " accumulated in the moving body, is represented by 

 the weight which it is capable of raising 1 foot high, and is equal to the weight of thf 

 moving body multiplied by the square of its velocity, and divided by twice the force of 



gravity, or , . 



-9 

 Thus, if a shot of 165 lbs. weight be moving with a velocity of 1470 feet per second, the 



" work " accumulated in it will be represented by 



1 65 X 1470 X 1470 , 



2 X 32 1908 



which is equal to 5538048 lbs., or 2472 tons. That is to say, the force stored up in this 



shot is capable of lifting a weight of 2472 tons 1 foot high. 



t See Table TIT. + See Tables in Appendix. 



