on Low-Temperature Research, 1893—1900. 715 



harder to take than the previous one. Among many causes of 

 augmenting difficulty is the circumstance that the molecular latent 

 heats of vaporisation diminish with the absolute boiling-point. 

 Hence, a continually more lavish expenditure of frigorific material is 

 necessitated, and of material the price of which, in money and labour, 

 rises rapidly with its frigorific efficacy. Still, although the bottom 

 of the temperature-scale may never be actually reached, the inter- 

 vening space will surely be much abridged. But we shall never, it 

 is safe to predict, assist at the " death of matter." At the stage 

 arrived at, there is no sign of its being moribund. Forces still act 

 within and upon it. Gravity and cohesion maintain their normal 

 power. It sensibly impedes the passage of electricity in the purest 

 and most highly conducting metals. Its minute particles can take 

 up and modify luminous vibrations. Only chemical affinity seems to 

 be extinct ; the various species of matter cease to react upon each 

 other. The next cryogenic achievement, it is true, may alter the 

 situation as we now see it. Our present standing-ground may be 

 subverted, for the inquiry is just now in a critical phase. The lique- 

 faction of helium, for example, may prove decisive of many things — 

 it may set at rest some doubts, and raise unlooked-for issues. 



The conditions for its accomplishment were clearly set forth in 

 the Bakerian Lecture. They may be realised by the use of methods 

 actually available. This last fortress of gaseity cannot be regarded 

 as impregnable, although its capture will be at a high monetary cost. 

 Gaseous helium, to begin with, is of the utmost scarcity ; and what 

 is scarce demands outlay to procure. Its condensation can be effected 

 only by subjecting it to the same process that succeeds with hydro- 

 gen, substituting, however, liquid hydrogen under exhaustion for 

 liquid air as the primary cooling agent. As the upshot, a liquid 

 will be at hand, boiling at about 5° absolute, or —268° C, but 

 more expensive than liquid hydrogen, in a much higher ratio than 

 liquid hydrogen is more expensive than liquid air. By comparison, 

 " potable gold " would be a cheap fluid. Nor could the precious 

 metal, in that, or any other form, be employed for a higher intel- 

 lectual purpose than in promoting and extending researches of such 

 boundless promise and commanding interest as those conducted at 

 the Royal Institution. 



List of Papers. 



1893 " Liquid Atmospheric Air." Proc. Koy. Inst. vol. xiv. p. 1. (Discourse 



delivered January 20, 1893.) 

 1893 "The Electrical Resistance of Metals and Alloys at Temperatures 



approaching the Absolute Zero." (With Professor J. A. Fleming.) 



Phil. Mag. vol. xxxvi. p. "271. See also Electrician, vol. xxxi. p. 529. 

 1S93 " Refractive Indices of Liquid Nitrogen and Air." (With Professor 



Liveing.) Phil. Mag. vol. xxxvi. p. 328. 

 1893 " Solid Atmospheric Air." Proc. Roy. Soc. vol. liii. p. 80. 

 1891 " Phosphorescence of Bodies at Low Temperatures." Proc. Roy. Soc. 



vol. lv. p. 340. 



