MEASURING THE STRIKING FORCE OF SHOT. 321 



double the diameter of those which made the deeper 

 penetration ; and whether the reasons I would ascribe 

 for these effects may or may not be correct, the broad 

 facts are in no wise altered, and no greater proof of 

 the inaccuracy of the system can be required. 



The efficiency of a force is estimated by the amount 

 of resistance it can overcome or the work it can do, 

 and in order to compare different forces we must have 

 uniform units of work. Now the targets used in the 

 gun-trials referred to are of a compound nature, paper 

 with an iron backing. " But no," some may say, 

 the paper is the target, and upon the paper alone is the 

 penetration made and recorded." Ah yes ! this is 

 where the penetration is recorded certainly ; but the 

 vast amount of force which is checked from further 

 jyenetration by the superior resistance of the iron is 

 not recorded, and here another error lies. By the trial 

 reports we are told the whole number of sheets op- 

 posed (40) were sometimes penetrated by one or two 

 pellets ; now, unless the iron backing is also indented 

 (which we are not informed of) this is impossible, 

 provided the paper pad is placed solidly and smoothly 

 against it, as we are assured it was intended to be ; and 

 so we must infer that the nature of the resistance 

 sometimes varied too, through neglect or inability to 

 comply with this regulation. These conclusions are 



