1920] on Researches at High Pressures and Temperatures 13 



tried which produced much higher instantaneous pressures than are 

 obtainable in any die. 



A rifle ■ 303 inch bore was arranged for withstanding a charge 

 of cordite 90 per cent, in excess of the service charge. 



The gun (Fig. 7) was fixed with its muzzle 6 inches from a 

 massive block of steel, in which a hole 0*303 inch in diameter had 

 been drilled to a depth somewhat greater than the length of the 

 bullet, and in alignment with the bore of the gun ; cylindrical 

 bullets of steel with a copper driving band were chiefly used, shorter 

 than the service bullet, and about one-half of the weight. The sub- 

 stance to be compressed was placed either at the bottom of the hole, 

 when a conical-nosed bullet of mild steel was used, or over the 



u 



muzzle of -303' n:n_E 



Fig. 



mouth of the hole, when a cupped-nose bullet of tool steel was 

 employed. About one hundred experiments were made. 



The substances tested included graphite, sugar carbon, bisulphide 

 of carbon, oils, etc., graphite and sodium nitrate, graphite and 

 fulminate of mercury, finely divided iron and fine carborundum, 

 olivine and graphite, etc. After each shot the bullet and surrouding 

 steel were drilled out, and the chips and entrained matter analysed. 

 Fig. 8 shows the bullet in the hole after firing. 



Several experiments were also made with a bridge of arc light 

 carbon placed over the hole and raised to the limit of incandescence 

 by an electric current, and the shot fired through it into the hole 

 at the moment the carbon commenced to vaporize, as observed in a 

 mirror from without. Also an arc between two carl tons was arranged 

 to play just over the hole, and the shot fired through it (Fig. 9), 



