578 



SCIENCE. 



[N. S. Vol. XVI. No. 406. 



present able to cope with the difficulties 

 involved in its production and collection. 

 Provided the critical point is, however, not 

 below eight degrees absolute, then from the 

 knowledge of the conditions that are suc- 

 cessful in producing a change of state in 

 hydrogen through the use of liquid air, we 

 may safely predict that helium can be 

 liqueiied by following similar methods. 

 If, however, the critical point is as low as 

 six degrees absolute, then it would be al- 

 most hopeless to anticipate success by 

 adopting the process that works so well 

 mth hydrogen. The present anticipation 

 is that 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 re- 

 sulting liquid would require to be col- 

 lected in a vacuum vessel, the outer walls 

 of which are immersed in liquid hydrogen. 

 The practical difficulties and the cost of 

 the operation Avill be very great; but on 

 the other hand, the descent to a tempera- 

 ture within five degrees of the zero Avould 

 open out new vistas of scientific inquiry, 

 which would add immensely to our knowl- 

 edge of the properties of matter. To com- 

 mand 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 tri- 

 umph for science. If the present Royal 

 Institution attack on helium should fail, 

 then we must ultimately succeed by adopt- 

 ing a process based on the mechanical pro- 

 duction of cold through the performance 

 of external work. "When a turbine can be 

 worked by compressed helium, the whole 

 of the mechanism and circuits being kept 

 surrounded by liquid hydrogen, then we 

 need hardly doubt that the liquefaction 

 will be effected. In all probability gases 

 other than helium will be discovered of 



greater volatility than hydrogen. It was 

 at the British Association 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 heliiun, and this antici- 

 pation was soon taken up by others and 

 ultimately confirmed. Later, in the Bak- 

 erian Lecture for 1901, I was led to infer 

 that another member of the helium group 

 might exist having the atomic Aveight 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 sopie such element or ele- 

 ments may yet be isolated and identified 

 as coronium or nebulium. If amongst the 

 unknown gases possessing a very low crit- 

 ical point some have a high critical press- 

 ure, instead of a low one, which ordinary 

 experience would lead us to anticipate, 

 then such difficultly liquefiable gases would 

 produce fluids having different physical 

 properties from any of those with which 

 we are acquainted. Again, gases may ex- 

 ist having smaller atomic weights and den- 

 sities 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 appa- 

 rently limited range of temperature which 

 separates solid hydrogen from the zero. 

 Indeed, gi'cat as is the sentimental interest 

 attached to the liquefaction of these refrac- 

 tory gases, the importance of the achieve- 

 ment lies rather in the fact that it opens 

 out new fields of research and enormously 

 widens the horizon of physical science, en- 

 abling the natural philosopher to study the 

 properties and behavior of matter under 

 entirely novel conditions. This department 

 of inquiry is as yet only in its infancy, but 

 speedy and extensive developments may be 

 looked for, since within recent years sev- 



