38 REPORT— 1902. 



the gas will succumb after being subjected to this process, only/instead of 

 liquid air under exhaustion being used as the primary cooling agent, liquid 

 hydrogen evaporating under similar circumstances must be employed. In 

 this case the resulting liquid would require to be collected in a vacuum 

 vessel, the outer walls of which are immersed in liquid hydrogen. The 

 practical difficulties and the cost of the operation will be very great ; but 

 on the other hand, the descent to a temperature within 5 degrees of the 

 zero would open out new vistas of scientific inquiry, which would add 

 immensely to our knowledge of the properties of matter. To command in 

 our laboratories a temperature which would be equivalent to that which 

 a comet might reach at an infinite distance from the sun would indeed 

 be a great triumph for science. If the present Royal Institution attack 

 on helium should fail, then we must ultimately succeed by adopting a 

 process based on the mechanical production of cold through the perform- 

 ance of external work. When a turbine can be worked by compressed 

 helium, the whole of the mechanism and circuits being kept surrounded 

 with liquid hydrogen, then we need hardly doubt that the liquefaction 

 will be effected. In all probability gases other than helium will be dis- 

 covered of greater volatility than hydrogen. It was at the British Asso- 

 ciation Meeting in 1896 that I made the first suggestion of the probable 

 existence of an unknown element which would be found to fill up the gap 

 between argon and helium, and this anticipation was soon taken up by others 

 and ultimately confirmed. Later, in the Bakerian Lecture for 1901, I was 

 led to infer that another member of the helium group might exist having- 

 the atomic weight about 2, and this would give us a gas still more volatile, 

 with which the absolute zero might be still more nearly approached. It 

 is to be hoped that some such element or elements may yet be isolated 

 and identified as coronium or nebulium. If amongst the unknown gases 

 possessing a very low critical point some have a high critical pressure, 

 instead of a low one, which ordinary experieiice would lead us to antici- 

 pate, then such difficultly liquefiable gases would produce fluids having 

 different physical properties from any of those with which we are 

 acquainted. Again, gases may exist having smaller atomic weights and 

 densities than hydrogen, yet all such gases must, according to our present 

 views of the gaseous state, be capable of liquefaction before the zero of 

 temperature is reached. The chemists of the future will find ample scope 

 for investigation within the apparently limited range of temperature 

 which separates solid hydrogen from the zero. Indeed, great as is the 

 sentimental interest attached to the liquefaction of these refractory gases, 

 the importance of the achievement lies rather in the fact that it opens out 

 new fields of research and enormously widens the horizon of physical 

 science, enabling the natural philosoplier to study the properties and 

 behaviour of matter under entirely novel conditions. This department 

 of inquiry is as yet only in its infancy, but speedy and extensive develop- 

 ments may be looked for, since within recent years several special cryo- 

 genic laboratories have been established for the prosecution of such 



