123 MR. H. WILDE ON THE 



vary more than a unit from the classical numbers. When 

 it is considered that some of these numbers have been 

 obtained by doubling the fractions of the old atomic 

 weights^ and that slight differences in the determinations 

 may arise from the latent affinity which some elements 

 have for minute quantities of another^ the numbers in 

 the tables are remarkably near to those determined by 

 experiment — more so in fact^ than is B ode's law to the 

 actual distances of the planets from the sun. 



It will be observed that there are gaps to be occupied 

 by two elements in the first group^ with atomic weights 

 154 and 177, and by their homologues of position in the 

 second group^ with atomic weights 160 and 184, which 

 remain to be discovered. 



, The numerical relations subsisting among the atomic 

 weights in Tables 11.^ III.^ and their resemblance to 

 homologous series in organic chemistry, afford further 

 evidence in support of the theory that elementary species 

 are formed by the successive condensations of a primordial 

 substance of small specific gravity and low atomic weight. 

 The physical and chemical properties of hydrogen^, 

 especially its low atomicity and its exact multiple relations 

 with many elementary substances, long since suggested to 

 Prout that this element might be the ponderable base of 

 all the others ^. Front's hypothesis has not, however, 

 made much progress, as chemical knowledge was not 

 sufficiently advanced in his time to enable the intermediate 

 steps to be perceived by which elements of high atomicity 

 could be built up from hydrogen ; and, besides this, the 

 hypothesis afforded no explanation of the widely diverging 

 properties of elements having nearly the same atomic 



* ' Annals of Philosophy,' vol. vi. p. 330 (1815) ; vol. vii. p. 113 (1816). 



