215 
the great abundance and wide distribution of iron in nature, 
it is probable that the vapour of this element would form a 
zone 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 propagated 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 palla- 
dium group appears to be more especially correlated with 
some particular member of the platinum group, and all are 
found associated together naturally in the metallic state. 
If the four members of the platinum group be considered 
the analogues of the corresponding members of the iron and 
palladium groups, it will be seen that one of the members 
of the latter group is missing. M. Sergius Kern, a Russian 
chemist, has recently discovered a new metal which he 
classifies with the platinum group, and has given to it the 
name of davyum.* The specific gravity of the new metal 
was found to be 9*39, and preliminary experiments on its 
equivalent show that it is greater than 100 and supposed to 
be 150 — 154. Now the specific gravity and atomic weight 
of the new metal exclude it from the platinum group, and 
also from the iron group of metals ; davyum is therefore the 
missing element in the palladium group, and will have a 
specific gravity of about 11, and an atomic weight of 105; or 
the same density and equivalent as the other members of 
the group. The state of aggregation of the small quantity 
of the new metal obtained by M. Kern, may have prevented 
the same specific gravity being found for it as for the other 
members. 
Although I have designated the highest members of the 
series Win, as the platinum group, yet if the slight differences 
* Comptes Kendus, tome lxxxv., 72, 623, 667. 1877. 
