THE ARTIFICIAL PRODUCTION OF DIAMOND. 



75 



Several experiments were made by substituting a tungsten -steel block, and a hole 

 tapering gently from 0'303-inch at the mouth to 0'125-inch at the bottom, and using 

 a mild steel bullet, which on entry would be deformed and a greatly increased 

 velocity imparted to the nose. Progressively increased charges were used, and even 

 with relatively small charges the block cracked on the second round. With the 

 90 per cent, excess charge, the block always split on the first shot, but this probably 

 occurred after impact, and not till the full instantaneous pressure had been exerted, 

 which was estimated to be greater than with the plain hole, probably over 5000 tons. 



Muzzle of 

 o-3O3"rifle 



Fig. 8. 



Only graphite was placed at the bottom of the hole in these latter experiments, 

 and the analysis yielded nothing. 



Experiments on Pressure in Cast Iron when Cooled. 



It has been generally assumed that iron rich in carbon expands on setting, and 

 that this supposed property is a contributory cause in the formation of diamond. 



Several experiments were made by pouring iron saturated with carbon from the 

 electric furnace through a narrow git into a very massive steel mould, closed at the 

 bottom with a breech screw (fig. 9). When cold, the breech screw was easily removed, 

 and there was no sign of any appreciable pressure having come on the threads. 

 Not being sure that, because of capillarity, the corners of the mould had been quite 

 filled, a steel mandril was, immediately after pouring, forced down the git-hole by a 

 press giving a fluid pressure in the mould of 75 atmospheres. The observed pressure 



VOL. ccxx. A. M' 



