1920] on Researches at High Pressures and Temperatures 15 



possible flame, that of acetylene and oxygen, with a slight excess of 

 the former to provide the carbon. The arrangement was as follows 

 (Figs. 10 and 11) : — A very light piston made of tool steel was carefully 

 fitted to the barrel of the gun of ■ 9-inch bore ; the piston was flat 

 in front, lightened out behind, and fitted with a cupped copper gas 

 check ring, the cup facing forward ; the total travel of the piston 

 was 36 inches. To the muzzle of the gun was fitted a prolongation of 

 the barrel formed out of a massive steel block, the joint being gas- 



Fig. 10. 



tight ; the end of the bore in the block was closed by a screwed-in 

 plug made of tempered tool steel, also with a gas-tight collar. A 

 small copper pin projected from the centre of the plug to give a 

 record of the limit of travel of the piston. The gun was loaded with 

 2 drachms of black sporting powder, which amount had been 

 calculated from preliminary trials. The barrel in front of the piston 

 was filled with the mixture of acetylene and oxygen. It was estimated 



Fig. 11. 



that this mixture would explode when the piston had travelled about 

 half wav along the bore ; when fired the piston travelled to within 

 i inch of the end, as had been estimated, giving a total compression 

 ratio of 288 to 1. As a result it was found that the surfaces of the 

 end plug, the fore end of the piston, and the circumference of the 

 bore up°to finch from the end of the plug had been fused to a 

 depth of about 0*01 inch, and were glass hard : the surface of the 

 copper pin had been vaporized, and copper sprayed over the face of 



