142 MR. H. WILDE ON THE 



liminary experiments on its equivalent show that it is 

 greater than loo 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 Hjn, as the platinum group, yet if the slight 

 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 

 respective groups being varieties of each other, that they 

 cannot by any known power of analysis be resolved into 

 their primaries, as the same objection would apply to the 

 natural varieties of organic species determined by natura- 

 lists. 



We have seen that the quantivalence of most of the 

 members of the preceding groups Hw, }16n, is in some 

 way correlated or dependent on the construction of the 

 typical molecules at the head of each series ; but in the 

 series Hyn the only element which is known to be septi- 

 valent is manganese, but the relation which this metal 

 has to the iron group, and bearing in mind that the 

 determination of the highest quantivalence of elements is 

 limited by the knowledge of chemists at particular times. 



