Chemistry and Physics. 153 



Substance. 18° to -78°. -78° to -188°. 188° to - 252° '5. 



Diamond 0*0704 0-0190 0-0043 



Graphite.- 0-1341 0-0599 0-0133 



Ice 0-463* 0-285 0*146 



" It appears from these values that between the ordinary tem- 

 perature and the boiling point of hydrogen the specific heat of 

 the diamond has been reduced to 1/19, whereas under similar 

 conditions graphite has diminished to about 1/10. Further it 

 will be observed that at the lowest temperatures the specific heat 

 of graphite is about three times that of the diamond. It is also 

 worthy of being recorded that the values of the specific heats of 

 diamond and graphite taken between the temperatures of liquid 

 air and boiling hydrogen are far smaller than that of any known 

 solid substance, being even lower than that of any gas taken 

 under constant volume." 



Another table gives the results obtained, at temperatures 

 extending down to —188°, for the specific heats of various sub- 

 stance including German-silver, brass, tellurium, sulphur, etc., to 

 solid carbon dioxide, solid ammonia and solid sulphur dioxide. 

 The author concludes with the remark that " an almost endless 

 field of research in the determination of specific heats is now 

 opened, in which the use of liquid air and hydrogen calorimeters 

 are certain to become ordinary laboratory instruments." 



2. On the Thermo-electric Junction as a Means of Determin- 

 ing the Lowest Temperatures; by Sir James .DEWAR.f — "The 

 inconvenience of using the gas thermometer at very low temper- 

 atures and the failure of platinum and other metal-resistance 

 thermometers within 30° or 40° of the absolute zero, led me some 

 years ago to consider the experimental behavior of the thermo- 

 electric junction at the lowest temperatures. My special object 

 at the time the experiments were made was to have a further 

 confirmation of the melting point of hydrogen, and also of the 

 lowest temperature reached on exhausting solid hydrogen, other 

 than that I had found by means of the hydrogen gas thermome- 

 ter. \ The results have remained unpublished, because my inten- 

 tion has always been to extend them to other thermo-electric 

 combinations. Not having been able to accomplish this project, 

 they are now abstracted as affording useful information in this 

 field of investigation, and as furnishing a general confirmation of 

 my previous investigations. 



A German-silver platinum couple was selected as likely to give 

 the most uniform results at low temperatures, although subse- 

 quent experiments have led to the conclusion that it would have 

 been better to have replaced the platinum by gold. As regards 

 resistance thermometers, I have shown that gold is more reliable 



* This from -18° to -78°. 



f Extracts from an advance proof (received from the author) of a paper 

 read June 8 before the Royal Society of London. 



% The Boiling Point of Liquid Hydrogen, determined by Hydrogen and 

 Helium Gas Thermometers, Proc. Roy. Soc, vol. lxxviii, 1901. 



