28 Mr. J. Brown on 



was frozen by Professor Dewar in 1893. A litre of liquid air 

 subjected to exhaustion in a silvered vacuum vessel yielded 

 about half a litre of a colourless, transparent solid, consisting of 

 a nitrogen jelly containing liquid oxygen. Solid oxygen is 

 obtained by subjecting liquid oxygen to cooling by immersion 

 of the tube containing it in boiling hydrogen. It is clear blue 

 ice. Solid hydrogen has been produced by the same kind ot 

 process. It is a transparent ice. 



The really important uses of liquefied gases are comprised in 

 their application to low temperature research, providing as 

 they do a means of cooling other bodies hitherto unattainable. 

 We may glance at a general view of this part of the subject. 

 It was at first supposed from the change in the electric 

 resistance of metals produced at this temperature that all 

 metals would become perfect conductors at absolute zero. 

 Further cooling by liquid hydrogen showed, however, that a 

 certain amount of resistance would still exist atO deg. absolute. 

 Phosphorescence is much increased by the cold of liquid air, 

 and much more by that of liquid hydrogen. Chemical affinity 

 is almost abolished by cold. Potassium, which bursts into 

 flame on water, remains inert on liquid air or oxygen. 



Fractionation by distillation at these low temperatures has 

 been effectively employed by Professor Ramsay and Dr. Travers 

 in 1898 for the extraction from the atmosphere of the new 

 gases, krypton, neon, and xenon, following on the discovery of 

 argon in 1895 by Lord Rayleigh, and helium later. 



In connection with the last mentioned, it is interesting to 

 recall how the name arose. In the spectroscopic examination 

 of the sun one line was observed which could not be detected 

 in any terrestrial substance. It was therefore supposed to be 

 peculiar to the sun, and so called the helium line. Subsequently, 

 however, it was proved to be like the other constituents of the 

 sun, terrestrial also, a gas more volatile than hydrogen, and 

 which has not yet been liquefied and solidified. 



The influence of very low temperatures an the vital force of 

 living organisms has also been examined. The cold of liquid air 



