1902.] Professor Bewar on Problems of the AtmosjpJiere. 223 



WEEKLY EVENING MEETING, 



Friday, April 11, 1902. 



The Eight Hon. Lord Kelvin, O.M. G.C.V.O. D.C.L. LL.D. D.Sc. 

 F.E.S., Vice-President, in the Chair. 



Professor Dewar, M.A. LL.D. D.Sc. F.R.S. M.B.L 



Problems of the Atmosphere. 



The present liquid ocean, neglecting everything for the moment but 

 the water, was at a previous period of the earth's history part of the 

 atmosphere, and its condensation has been brought about by the 

 gradual cooling of the earth's surface. This resulting ocean is sub- 

 jected to the pressure of the remaining uncondensed gases, which 

 for the present we may regard as composed solely of nitrogen and 

 oxygen, and as these are slightly soluble they dissolve to some extent 

 in the fluid. The gases in solution can be taken out by distillation 

 or by exhausting the water, and if we compare their volume with 

 the volume of the water as steam, we should find about 1 volume of 

 air in 60,000 volumes of steam. This would then be about the 

 rough proportion of the relatively permanent gas to condensable gas 

 which existed in the case of the vaporised ocean. 



Now let us assume the surface of the earth gradually cooled to 

 some 200 degrees below the freezing-point; then, after all the present 

 ocean was frozen, and the climate became three times more intense 

 than any arctic frost, a new ocean of liquid air would apjiear about 

 thirty- five feet deep, covering the entire surface of the frozen globe. 



We may now apply the same reasoning to the liquid air ocean 

 that we formerly did to the water one, and this would lead us to 

 anticipate that it might contain in solution some gases that may be 

 far less condensable than the chief constituents of the fluid. lu order 

 to separate them we must imitate the method of taking the gases out 

 of water. 



If a sample of liquid air cooled to the lowest temperature that 

 can be reached by its own evaporation was connected by a pipe to 

 a condenser cooled in liquid hydrogen, the result would be rapid 

 distillation, and any volatile gases present in solution would distil 

 over with the first portions of the air, and while the nitrogen and 

 oxygen solidified in the condenser they could be pumped ott, being 

 still gaseous at the temperature of 20° absolute. A diagram of the 

 apparatus is given in my lecture entitled "Gases at the Beginning 

 and End of the Century."* In this way, a gas mixture, containing, 

 of the known gases, free hydrogen, helium and neon, has been 

 separated from liquid air. 



* Proceedings of the Eoyal Institution, Vol. XVI. p. 736. 



