On the Constitution of Atmospheric Neon, 449 



Thus 



E= ^ 



/^R^l-^sin 2 ^)!' 



Ri is the unit vector along e j P', and 



H = vE sin\ lt 



These results are of course well known, but T think it will 

 be admitted that the above is a particularly easy way of 

 obtaining them. By extension of the principle described 

 to quaternionic operators it is evident that the whole of the 

 theory of Relativity can be very conveniently expressed in 

 this notation. 



In conclusion I should like to express my thanks to 

 Dr. Silberstein for reading my paper and for his interest 

 in it. 



XLIV. The Constitutio)i of Atmospheric Neon. By F. W. 

 Aston, M.A., D.Sc, Clerk Maxwell Student of the Uni- 

 versity of Cambridge* . 



[Plates VIII. & IX.] 



IN periodic tables of the elements arranged in order of 

 their atomic weights the part lying between Fluorine on 

 the one hand and Sodium on the other is of considerable 

 interest. 



Soon after the discoverv of argon and while the mon- 

 atomic nature of its molecule was still under discussion, 

 Emerson Reynolds, in a letter to 'Nature' (March 21, 

 1895), described a particular periodic diagram which he had 

 used with advantage. In this letter, referring to the occur- 

 rence of the groups Fe, Ni, Co: Ru, Rh, Pd: and Os, Ir, Pt, 

 the following passage occurs : — 



kt . . . . the distribution of the triplets throughout the whole 

 of the best known elements is so nearly regular that it is 

 difficult to avoid the inference that three elements should 

 also be found in the symmetrical position between 19 and 

 23, i. e. between F and Na, .... of which argon may be 

 one . . . ." 



In 1898 neon was isolated from the atmosphere, in which 

 it occurs to the extent of "00123 per cent, by volume, by 



* Communicated by the Author. 

 Phil. Mag. Ser. 6. Vol. 39. No. 232. April 1920. 2 G 



