36 REPORT— 1902. 



by cold in the same proportion as at temperatures about minus 200 degrees. 

 This being the case, there is no longer any reason to suppose that at the 

 absolute zero platinum would become a perfect conductor of electricity ; 

 and in view of the similarity between the behaviour of platinum and that 

 of other pure metals in respect of temperature and conductivity, the pre- 

 sumption is that the same is true of them also. At any rate, the know- 

 ledge that in the case of at least one pi'operty of matter we have succeeded 

 in attaining a depth of cold sufficient to bring about unexpected change 

 in the law expressing the variation of that property with temperature, is 

 sufficient to show the necessity for extreme caution in extending our infer- 

 ences regarding the properties of matter near the zero of temperature. 

 Lord Kelvin evidently anticipates the possibility of more remarkable elec- 

 trical properties being met with in the metals near the zero. A theoretical 

 investigation on the relation of 'electrions' and atoms has led him to sug- 

 gest a hypothetical metal having the following remarkable properties : below 

 1 degree absolute it is a perfect insulator of electricity, at 2 degrees it shows 

 noticeable conductivity, and at 6 degrees it possesses high conductivity. It 

 may safely be predicted that liquid hydrogen will be the means by which 

 many obscure problems of physics and chemistry will ultimately be 

 solved, so that the liquefaction of the last of the old permanent gases is 

 as pregnant now with future consequences of great scienti6c moment as 

 was the liquefaction of chlorine in the early years of the last century. 



The next step towards the absolute zero is to find another gas more 

 volatile than hydrogen, and that we possess in the gas occurring in clevite, 

 identified by Ramsay as lielium, a gas which is widely distributed, like 

 hydrogen, in the sun, stars, and nebula\ A specimen of this gas was 

 subjected by Olszewski to liquid air temperatures, combined with com- 

 pression and subsequent expansion, following the Cailletet method, and 

 resulted in his being unable to discover any appearance of liquefaction, 

 even in the form of mist. His experiments led him to infer that the 

 boiling-point of the substance is probably below 9 degrees absolute. 

 After Lord Rayleigh had found a new source of helium in the gases which 

 are derived from the Bath springs, and liquid hydrogen became available 

 as a cooling agent, a specimen of helium cooled in liquid hydrogen showed 

 the formation of fiuid, but this turned out to be owing to the presence of 

 an unknown admixture of other gases. As a matter of fact, a year 

 before the date of this experiment I had recorded indications of the 

 presence of unknown gases in the spectrum of helium derived from this 

 source. When subsequently such condensable constituents were removed, 

 the purified helium showed no signs of liquefaction, even when com- 

 pressed to 80 atmospheres, while the tube containing it was sur- 

 rounded with solid hydrogen. Further, on suddenly expanding, no 

 instantaneous mist appeai-ed. Thus helium was definitely proved to be a 

 much more volatile substance than hydrogen in either the liquid or solid 

 condition. The inference to be drawn from the adiabatic expansion 

 efiected under the circumstances is that helium must have touched a tempe- 



