4 Wilde, Atomic Weights^ Neon and Heliuiu. 



The remarkable resemblance which the members of 

 the iron group have to each other while their atomic 

 weights are nearly the same, has long been a subject of 

 interest to philosophical chemists, and if the views which 

 I have enounced respecting the formation of elementary 

 species be correct, the cause of these resemblances admits 

 of a possible explanation. 



From the great abundance and wide distribution of 

 iron in nature, it is probable that the vapour of this 

 element would form an atmosphere of considerable depth ; 

 the upper and lower regions of which, by differences of 

 pressure and temperature, might produce allotropic 

 varieties before a definite change to the next higher 

 members in the series occurred. When once varieties of 

 an element were formed, these varieties would be propa- 

 gated through successive condensations into the next 

 higher members of the series, just as they are found in 

 the palladium and platinum groups of metals. Chemists 

 have already observed that each of the metals of the 

 palladium group appears to be more especiall}' correlated 

 with some particular member of the platinum group, and 

 all are found associated together naturally in the metallic 

 state. M. Sergius Kern, a Russian chemist, has discovered 

 a new metal with an approximate specific gravity of 9-39 

 which he classifies with the platinums, and has given to it 

 the name of Uavyum.- The low specific gravity of this 

 element indicates it as the fourth member of the palladium 

 group of metals, as shown in my general Tabic. 



The chief properties which distinguish the elements 

 of the series Hyw are their high fusing-point and their 

 passivity in the presence of ordinary reagents, to which 

 iron, under peculiar conditions, forms no exception. 



Although gold in some recent classifications of ele- 



* Coiiiptes Reiuiits, tome S5, pp. 72, 623, 667. 



