Manchester Memoirs, Vol. Ivii. (19 1 3), ^0. \%. 5 



ments has been separated from the platinum metals, yet, 

 in its primary qualities, it exhibits closer analogies with 

 them than with the members of any other series, and 

 there is no other place vacant in the groups which an 

 element with the atomic weight and physical properties of 

 gold would fit. The constant association in nature of 

 quartz, hematite, and specular iron ores with gold and 

 platinum is a fact fully recognised by chemical geologists* 

 and confirms the positions assigned for Si, Fe, and Au, in 

 the table as forms of H7;a 



Although I have designated the highest members of 

 the series W'jn as the platinum group, yet if the small 

 differences in their atomic weights and physical properties 

 admit of explanation by the assumption of their being 

 allotropic varieties of each other, then gold, palladium and 

 iron may stand at the head of their respective groups and 

 determine the species to which the varieties belong. It is 

 no objection to the theory of the members of the respec- 

 tive groups being varieties of each other that they cannot 

 by any known power of analysis be resolved into their pri- 

 maries, as the same objection would apply to the natural 

 varieties of organic species determined by naturalists. 



The arbitrary policy of several writers in doubling the 

 atomic weights of four of the gaseous members of the 

 series H/w, viz.: neon, argon, krypton and xenon, (not- 

 withstanding that the atomic weights of nitrogen, hydro- 

 gen, oxygen and chlorine are the same as their specific 



* Bischoft's Cheaiical and Physical Geology, Vol. 3, p. 534. 

 Cavendish Soc. Works. Murchison's Siluria, Chap. 17, pp. 433.439- 



