128 MR. H. WILDE ON THE 



While the property of quantivalence would appear to 

 be correlated with the number of hydrogen particles in 

 the typical molecules from which the elements were 

 evolved, and is a valuable aid in the classification of ele- 

 mentary species, this property, in the present state of 

 knowledge, is not in many cases sufficient, of itself, to 

 indicate the group to which an element belongs. This 

 will be seen from the recognized bivalency of copper and 

 mercury, and by the doubtful quantivalence of silver, and 

 by analogy of sodium, all of which belong to the series 

 Hn. That tetratomic lead = 208, is a member of the 

 group H2W, is shown by the isomorphism of its oxide, 

 carbonate, and sulphate, with the oxides, carbonates, and 

 sulphates of barium, strontium, and calcium ; besides 

 which there is no other place vacant in the system of ele- 

 ments where one with the atomic weight and physical 

 properties of lead would fit. 



Were it not for the analogous physical properties and 

 the numerical relations subsisting among the elements 

 grouped as forms of H3W, their classification from the 

 property of quantivalence alone would hardly have been 

 possible. There can, however, be little doubt that alumi- 

 num, yttrium, erbium, and thorium are rightly classified 

 together, and that indium and thallium are true analogues 

 of each other. As considerable interest attaches to this 

 group at the present time, on account of the recent addi- 

 tions which have been made to it by the aid of spectral 

 analysis, I here show the atomicities of its members in a 

 separate Table, calculated on the same principle as those 

 in Tables II., III. 



