Manchester Memoirs, Vol. Ivii. (1913;, No. 1^. 7 



it is incumbent on me to say that no teacher of natural 

 science, with the above table before him, is at liberty to 

 double the atomic weights of the inert gases of the series 

 Yiyn without violence to his moral intelligence and lasting 

 injury to the ingenuous student who looks up to him for 

 guidance and instruction. These remarks are equally 

 applicable to the doubling of the atomic weight of helium, 

 which element has been separated from the series H2;/, 

 and grouped with Ne, Ar, Kr, Xe, solely on account of its 

 chemical inertness, the five elements having no other 

 rational classification. 



It is a common error to assume that discoverers in 

 various departments of science are, necessarily, authorities 

 on the co-ordination of the subject of their discoveries 

 with the general properties of bodies, and with the real 

 nature of things. Thus (i) Peligot adopted 120 as the 

 atomic weight of uranium, and Stromeyer 56 for cadmium, 

 the modern determinations for these elements being 240 

 and 112 respectively. (2) Scheele's oxymuriatic acid was 

 shown by Davy to be elementary chlorine. (3) Platinum 

 was identified by its Brazilian discoverer with silver, and 

 derived its name from that metal. Many similar instances 

 may be adduced from other departments of the natural 

 sciences. It will be sufficient to mention in this con- 

 nexion the discovery and first appearance of Saturn's 

 rings, the supposed cometary nature of the planet 

 Uranus, and the landfall of Columbus. 



Helium, as will be seen in several of my papers, is the 

 typical element of the series H2«, with an atomic weight 

 of 2 (He = 2) as shown in the following table. This 

 number has been adopted by French chemists in the table 

 of atomic weights published in the Annuaire dn Bureau 

 des Longitudes. 



