on Low- Temperature Research, 1893-1900. 713 



could be regarded as even probable. Instances of agreement witb tbe 

 auroral spectrum were also adverted to; and some are likely to prove 

 genuine. In tbis direction, certainly, lies tbe best bope of elucidating 

 tbe baffling problem of tbe " Northern Ligbts." 



By tbe use of liquid hydrogen as an analytic agent, neon can be 

 spectroscopically distinguished through its yellow line at A. 5853, in 

 25 cubic centimetres of ordinary air. The searching nature of the 

 method may be estimated from the consideration that the proportion 

 of tbe gas present is only one in 40,000. The fundamental neon-line, 

 indeed, predominates in the spectrum of tbe atmospheric residuum, 

 very much as the adjacent ray of helium does in the prismatic light 

 emanating from tbe more volatile portion of the Bath gas. Both 

 rays shine in each spectrum, but with reversed brilliancy. Professor 

 Dewar's inquiries thus confirmed the status of helium as an invariable 

 atmospheric constituent. They, moreover, demonstrated the associa- 

 tion witb it of hydrogen. In every sample of air there is a percentage 

 of hydrogen. The ratio by volume, according to M. Armand Gautier's 

 recent determination, is 1 to 5000. If, then, as Dr. Johnstone 

 Stoney maintains, the velocities of its molecules are, in tbe long run, 

 uncontrollable by gravity, tbe leakage thence ensuing must be com- 

 pensated either from within or from without. Subterranean sources 

 perhaps supply the deficit ; or interplanetary space itself gives back 

 as many vagrant molecules as it receives. A balance, at any rate, is 

 evidently struck somehow. 



In a later communication to tbe Royal Society (read June 20, 

 1901), Professors Liveing and Dewar dealt with the least volatile, as 

 they had previously dealt with the most volatile of the atmospheric 

 gases. Separated from liquid air by careful processes of distillation, 

 xenon and krypton were submitted to spectroscopic examination, in 

 the course of which tbe variations of their spectra with the character 

 of the electric discharge attracted particular attention. The rays of 

 xenon measured and tabulated numbered 257, those of krypton, 182. 



Low Temperature and Vital Phenomena. 



Low-temperature research is of extreme importance to the study 

 of vital phenomena. Our ideas as to the nature of life, and our con- 

 jectures regarding the course of its history on this planet, must be 

 largely regulated by experience of its capability to resist extremes 

 of heat and cold. Now tbe upper limit of endurance is easily reached ; 

 it is never above, and is usually considerably below +100° C. ; but 

 germicidal cold has not yet been produced. Warm-blooded animals, 

 to be sure, necessarily perish, and perish promptly, under frigid con- 

 ditions. The power of resistance, however, increases with simplicity 

 of organisation ; and the ultimate atoms of life (so to call bacteria) 

 bear witb impunity an indefinite amount and degree of freezing. 

 Professor M'Kendrick found, in 1893, that sterilisation did not result 

 from an hour's exposure to a temperature of — 182° C. Samples of 



