1920] on Researches at High Pressures and Temperatures 9 



pole is electrically insulated from the container by vulcanized fibre 

 washers and a rubber cup ring, which is protected from the heat by 

 magnesite stemming. 



The current is conveyed from the container to the top pole piece 

 of the conductor by pads of copper gauze which can slide easily 

 against the bore of the container and allow for the expansion of the 

 conductor. Experiments on liquids with this container under 4400 

 atmospheres gave the same results as my former experiments under 

 2200 atmospheres. 



THIN PRESSfAHN 



InsuUtion 



g= BRASS CUP 

 PACKING 



ru9be.b cup 

 Packing 



VUlCamjxeo Fisfz Ring 



Fig. 4. 



Fig. 5 shows the container arranged to melt graphite under 

 pressure by resistance heating. Here the charge is graphite, and is 

 divided by the bridge or ring made of pressed calcined magnesia or 

 of titanium oxide. The bore of the container is electrically insu- 

 lated from the graphite by layers of asbestos millboard and mica. 



The calories evolved in the combination of graphite and oxygen 

 are about half of 1 per cent, less than those evolved in the combina- 

 tion of diamond and oxygen, indicating that graphite at ordinary 

 temperature is to this extent the stable state. The bulk pressure 

 which has operated in some of the experiments would, however, seem 

 to have been amply sufficient to turn the balance in favour of diamond 

 instead of graphite. The uncertainty, on the other hand, as to the 

 compressibilities and specific heats of the allotropic forms of carbon 



