10 



The Hon. Sir Charles Parsons 



[Jan. 23, 



under high pressures and at high temperatures renders speculation 

 of little value as to what may occur at the melting point of carbon. 

 All we know is, that up to the pressures and temperatures reached in 

 our experiments no indication of a change from graphite to diamond 

 has been produced. In one experiment very intense heating was 

 applied for five seconds, hut sufficient in amount to melt the graphite 

 core six times over, the only result being a slight alteration of the 

 Btructure of the graphite ; the barrier in this experiment was calcined 

 magnesia, and the hole in it was superficially converted to magnesium 

 carbide. It appeared, however, desirable further to investigate the 

 possibility of carbon losing its electrical conductivity when approach- 



vulcanized 

 Fibre Ring 



Fig. 5. 



ing its melting point, as alleged by Ludwig and others, and of 

 Bhunting the current from itself on to the contiguous molten layers 

 of the insulating barriers surrounding it. There had been no indica- 

 tion of such a change having occurred, even momentarily : it rather 

 seemed that the graphite core had been partially vaporized and con- 

 densed in the cooler parts of the charge. The experiment was 

 repeated with rods of iron and tungsten embedded in the core, so 

 that should the temperature of volatilization of the metals under a 

 pressure of 15,000 atmospheres exceed that necessary to liquefy 

 carbon under the same pressure, the presence of these metals might 

 produce a different result. No change however occurred. 



