186 



ELEMENTARY PRINCIPLES OF GUNNERY. 



water, the rifles to be tried are fired at them from a distance 

 usually of 200 yards, the penetration being estimated by the 

 number of planks pierced. Three rounds are fired from each 

 rifle, and the average of the three shots is taken to be the 

 penetrating power of that particular rifle. The force of dif- 

 ferent kinds of gunpowder is estimated in the same way, using 

 one rifle and similar bullets and charges of powder. The 

 machine for private purposes may be made entirely of wood, 

 and is then within the reach of every sportsman; but the 

 elm boards of course require constant renewal as they are 

 shot to pieces. In trying these experiments, the result should 

 be recorded in a tabular form, as follows : 



Which will always give the result at one glance, without the 

 necessity for a written description. In the military trials 

 the amount of perforation, if any, in the last board is also 

 expressed in tenths : thus, first shot, 13'1 j second shot, 12*4; 

 third shot, 14'1 average, 13*2. 



EPROUVETTES. 



The above are the most correct modes of estimating the explosive 

 force of powder, but the former is seldom used, on account of 

 the complicated nature of the calculations required, and of 

 the necessity for the impingement of the ball upon the 



