THE GASES OF THE ATMOSPHEEE 145 



The differences between the extremes are as follows : 



Manganese Fluorine - - 36 



Chromium Oxygen - 36 '3 



Vanadium Nitrogen ! -; - 37*4 



Titanium Carbon - - 36*1 



Scandium Boron - - 33*1 



Calcium Glucinum - 31 



Potassium Lithium " - - 32 '1 



Argon Helium - - 36 



These differences are not very far from 36. 



I believe therefore that an element hitherto unknown should 

 find a place between helium and argon. We have looked for 

 this element in vain. However, we have not given up the 

 search, and if we succeed the discovery would throw much light 

 on the nature of helium and argon." 



In September 1897 the meeting of the British Associ- 

 ation took place at Toronto in Canada, and Ramsay was 

 President of the Chemical Section. The customary 

 address was occupied chiefly with an exposition of the 

 relations of helium and argon very nearly on the lines 

 of the summary just given. 



With these considerations as a guide the discovery of 

 an elementary gas, having a density 10 and atomic 

 weight 20, was foretold. This prophecy, however, was 

 not realised till a year later, when Ramsay and Travers 

 announced in June 1898 the discovery of a new gas in 

 the least volatile portion of a large quantity of liquid 

 air. This gas they named krypton (hidden). A fort- 

 night later they discovered another gas called neon (new), 

 which was found to possess the density required for the 



