The Hon. Sir Charles Parsons 



[Jan. 23, 



1 I 



The residues were in all cases exceedingly small, and there was no 

 evidence of any incipient transformation of carbon in bulk into 

 diamond thai could be detected by analysis. 



The pressure on impact of a steel bullet fired into a hole in a 

 steel block which il tits is limited by the co-efficient of compressibility 

 f gteel; with a velocity of 5< >0M I feet seconds it is about 2000 tons 

 per Bquare inch. Measurements made from a section through the 

 block and bullet (Fig. 8) showed that the mean retardation on the 

 frontal face after the impact till it had come to rest was about 

 600 tons per square inch. Several experiments were made by 

 substituting a tungsten steel block hardened and tempered ^ and a 

 hole tapering gently from 0*303 inch at the mouth to 0*125 inch at 

 the bottom/ The mild steel bullet was deformed by the tapered hole, 

 which greatly increased the velocity imparted to the nose. Progres- 

 sively increased charges were used. With the 90 per cent, excess 

 charge the Mock always split on the first shot, but this probably 



Muzzle of -303 



Fig. 9. 



occurred after impact, and not till the full instantaneous pressure 

 had been exerted, which was probably about 5000 tons per square 

 inch, or about equal to that at the centre of the earth. 



It would be interesting to repeat some of these experiments on 

 a larger scale. With a projectile of 6 inches or 9 inches in diameter and 

 a velocity of 5000 feet seconds, the instantaneous pressure would be 

 the same, but its duration (which is proportional to the linear 

 dimensions) would be increased from 20 to 30 fold. It has been 

 estimated that the rise in temperature due to adiabatic compression of 

 incandescenl carbon when subjected to 2000 tons per square inch is 

 of the order of about 1000° C, so that actual melting of the carbon 

 would probably have occurred when the shot was fired through the 

 incandescent carbon bridge. 



Another experiment was arranged which would ensure that carbon 

 should be subjected to an extremely high temperature concurrently 

 with high pressures, obtained by the rapid compression of the hottest 



