552 Mr. Richard Threlfall [March 19, 



carbon rods were heated by electricity under a pressure usually 

 of 15 tons per sq. inch — but rising in one case to 30 tons per sq. 

 inch. The pressure was obtained by means of a hydraulic press, but 

 no detail is given. 



I have been desirous for many years of making some experiments 

 at high temperatures and pressures, but for a long time could think 

 of no way of ascertaining the pressure at temperatures over a red 

 heat except by the use of compressed gases. In 1902 Sir Andrew 

 Noble was kind enough to have some drawings prepared for a wire- 

 wound steel pressure vessel to carry a pressure of 50 tons per sq. 

 inch. The pressure was to be supplied by a compressed gas, and 

 some details of the heating arrangements wei-e designed, when a 

 calculation of the cost of the gas compressors, vessel and appurten- 

 ances made it clear that the undertaking would be beyond my means. 

 I then endeavoured to find a simpler form of apparatus, and finally 

 was led to contemplate the substitution of graphite for compressed 

 gas, Spring having pointed out that crystalline graphite flows very 

 easily at high pressures. A simple trial made it clear that the 

 graphite of Ceylon does in fact possess the property of flowing like 

 a liquid under high pressure to a sufficient degree to allow of pressure 

 being transmitted by it. Graphite can be used with some reserva- 

 tions to transmit a pressure just like water or oil, though it is, of 

 course, inferior in fluidity, and as I have now discovered occasions a 

 loss of " head " which is not independent of the pressure itself. My 

 former statement in the 'Chemical Society's Journal,' 190'S, is erro- 

 neous, though the results of the experiments are, I believe, hardly or 

 not at all affected by the mistake for a reason which will be clear 

 later on. After several trials, the apparatus which I have here 

 to-night was evolved, and some experiments were made with it. 

 These experiments are not of any great importance, and, indeed, 

 I feel almost ashamed of bringing them to your notice — I can only 

 say in excuse that everything must have a beginning. 



I believe, however, that the apparatus is sufficiently simple, cheap, 

 and effective, to enable others with more leisure at their disposal to 

 make a beginning of an investigation of the properties of matter up 

 to 100 tons per sq. inch, and at temperatures up to about 2000° C. 

 At present, however, it is not possible to infer with accuracy the 

 volume of the substance under these extreme conditions, nor can its 

 physical condition be more than approximately and indirectly inferred 

 — we must content ourselves with the production of transformations 

 which we can make persist down to ordinary temperatures and pres- 

 sures. 



If we refer again to the sulphur diagram, we shall see how this 

 possibility may arise. If sulphur is melted and cooled slowly mono- 

 clinic crystals are found — when the temperature sinks below 98° C. 

 these crystals undergo spontaneous transformation to the rhombic 

 form — but all that we see is that the monoclinic crystals become 



