CHAPTER V 

 THE GASES OF THE ATMOSPHERE 



THE last twenty years of the nineteenth century wit- 

 nessed two discoveries in physical science, namely the 

 observation of X rays and the isolation of the argon 

 series of gases, which equal, if they do not surpass, in 

 significance and interest the discoveries of any previous 

 period. Of the two the latter must be regarded as the 

 most surprising, because it was not only unexpected, 

 but the existing evidence would have appeared con- 

 clusive against the possibility of such a discovery as 

 that of a new unheard-of constituent of our atmosphere. 

 It is, however, an interesting illustration of a statement 

 made by Lord Kelvin in his Presidential Address to the 

 British Association in 1871 : " Accurate and minute 

 measurement seems to the non-scientific imagination a 

 less lofty and dignified work than looking for something 

 new. But nearly all the grandest discoveries of science 

 have been but the rewards of accurate measurement 

 and patient long-continued labour in the minute sifting 

 of numerical results." For the discovery originated in 

 the laborious and accurate determination by Lord Ray 



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