Chemistry and Physics. 309 



them also. At any rate, the knowledge that in the case of at least 

 one property of matter we have succeeded in attaining a depth of 

 cold sufficient to bring about unexpected change in the law express- 

 ing 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 tempera- 

 ture. Lord Kelvin evidently anticipates the possibility of more 

 remarkable electrical properties being met with in the metals near 

 the zero. A theoretical investigation on the relation of " elec- 

 trions" and atoms has led him to suggest 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 scientific moment as was the lique- 

 faction 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 cleveite, identified by Ramsay as helium, a gas which 

 is widely distributed, like hydrogen, in the sun, stars and nebulae. 

 A specimen of this gas was subjected by Olszewski to liquid air 

 temperatures, combined with compression and subsequent expan- 

 sion, 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 ot helium in the 

 gases which are derived from the Bath springs, and liquid hydro- 

 gen became available as a cooling agent, a specimen of helium 

 cooled in liquid hydrogen showed the formation of fluid, 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 ot 

 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 compressed to 80 atmospheres, while the tube contain- 

 ing it w^as surrounded with solid hydrogen. Further, on suddenly 

 expanding, no instantaneous mist appeared. Thus helium w^as 

 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 effected under the 

 circumstances is that helium must have touched a temperature of 

 from 9 to 10 degrees for a short time Avithout showing any signs 

 of liquefaction, and consequently that the critical point must be 

 still lower. This would force us to anticipate that the boiling- 

 point of the liquid will be about 5 degrees absolute, or liquid 



