DETONATION OF HIGH EXPLOSIVES OR BY THE IMPACT OF BULLETS. 441 



is shown in the curve fig. 5. The hullets were almost precisely alike both in regard 

 to total weight (0'0306 Ibs.) and distribution of weight along the length. 



Most of the experiments were made with the service cartridge, in the service rifle, 

 giving an average velocity of 2000 feet per second. These cartridges were very 

 uniform, the range of variation in velocity being under one per cent. Some 

 experiments were also made with cartridges giving velocities of about 1240 feet per 

 second and 700 feet per second respectively. 



The rod against which the bullet was fired was in most cases of steel containing 

 C, 0'4 per cent. ; Mn, 1'05 per cent. Its breaking strength was 37 tons per square 

 inch with 24 per cent, elongation over 8 inches. The end of the rod was heated to a 

 white heat in the forge and quenched and would then stand a large number of shots 

 without serious damage. In some cases tool steel hardened, and tempered blue, was 

 used, but it was found difficult to get the temper exactly right. The pieces butted to 

 the end of the rod were usually of mild steel. For recording the movement of the rod 

 and of the box in which the piece was caught each was fitted with a pencil which 

 moved over a horizontal sheet of paper and the length of the mark was measured. 



Assuming that the bullet strikes the rod fairly in the centre, and that the 

 fragments are shot out radially, the total momentum recorded in rod and piece should 

 be equal to the momentum of the bullet, which at 2000 feet per second is 61 "2 Ib. feet 

 per second units. In fact, considerable variations were found in the total momentum. 

 For instance, in 110 shots fired at a 1-inch rod, the maximum total recorded was 76, 



100 



60 



40 



Fig.6. 



Length of piece , Inches 



the minimum 50, and the average 63. With a rod of l inches diameter, the 

 variation was less ; 61 shots showed a minimum of 59, a maximum of 70, and a mean of 

 62-5 High values are probably due to fragments being thrown back by irregularities 

 in the surface of the rod, low values to slight errors in aiming. It was found, 

 however, that with a piece of given length, the total momentum was shared between 

 the piece and the rod in a nearly constant proportion, though the 



VOL. CCXIII. A. 3 L 



