412 RiiroKT — 1866. 



where 



AY=Aveight of shot in lbs. 

 V = velocity on impact in feet. 

 ^= gravity. 

 2K= diameter of shot in feet. 

 h = thickness of unbacked plate in feet. 



7.;= a coefficient depending on the nature of the wrought iron in the 

 plate, and the nature and form of the head of shot. 

 The shot is supposed to be of the best quality of steel, and the plate of 

 the best quality of wrought iron. 



>Solving the equation (1) for b, we have 



(^) 



and for I', 



^^ (3) 



In order to determine /.;, we can form a series of ecjuations of the follow- 

 ing conditions : — 



&c. &c. &c. 



Substituting the experimental values of the different quantities, and eli- 

 minating /.-, we find that for hemispherical-headed shot 



7.-= 53.57200. 



Having thus determined the value of 1-, we can calcidate the " work " 

 necessary to penetrate any unbacked plate of given thickness. 



Thus, let US determine the " work " required to just penetrate a 5-5-inch 

 plate M'ith a hemispherical-headed steel shot of (r22 inches cUameter. 

 Here we have 



E=3-ll inches = 0-2591 7 feet, 

 7; =5-5 inches =0-45833 feet, 

 A~5357200 ; 



and substituting these values in equation (1), we find that 



^'=1832522 lbs. 



= 818 foot-tons. 



We see that round 1008, consisting of a spherical shot of 35-56 lbs. and 

 6-22 inches diameter, moving with a velocity of 1829 feet, and consequent 

 " work " of 825 foot-tons, just penetrated a 5-5-inch plate. This " work " is 

 practically the same as that given in the above example, as a difference of 5 ozs. 

 in the weight of the shot would have reduced its work to 818 foot-tons. 



By means of the foregoing eqiiations, wc can determine most of the effects 

 against unbacked plates ; and the following examples are given in proof. 



Example I. — What thickness of unbacked wrought-iron plate will with- 

 stand the impact of a soUd hemispherical-headed steel shot of 115 lbs. weight, 

 and 0-92 inclies dinmctor, fired with a charge of 22 lbs. from the 7-inch 

 ML rifled A\''oolwich gun at 1000 yards, remaining velocity at that distance 

 ijeing 1260 feet ? 



