108 PROGRESS OF SCIENCE IN THE CENTURY. 



it has often been felt that the boon would be great 

 if we could arrange the different kinds of matter in 

 groups or series corresponding in some measure to 

 the classes, orders, families, etc., in which we ar- 

 range plants and animals. 



It is therefore hardly necessary to say that Men- 

 delejeff was not the first to be attracted by the possi- 

 bility of detecting serial relations among the chem- 

 ical elements. Apart from the speculations of the 

 ancients and of the alchemists, glimpses of a sup- 

 posed orderly relationship of the various elements 

 seem to have been frequent in the history of chem- 

 istry. Particularly noteworthy was the idea of a fun- 

 damental substance, " protyle ^' or " prothyle,'' often 

 identified with hydrogen, of which the other elements 

 were supposed to be derivatives. Prof. Tilden sums 

 up the idea in the quotation: — 



" All things the world which fill 

 Of but one stuff are spun." 



More concretely, the hypothesis was hazarded anony- 

 mously by Prout (1815) that the atomic weights 

 of the gaseous elements are all whole multiples of 

 hydrogen. And with this view, supported by Mei- 

 necke (1817), was involved the suggestion that the 

 various elements might turn out to be derivatives 

 of one primary form of matter, such as hydrogen, 

 or something of which hydrogen was an atomic 

 multiple. It was an evolutionist speculation, but 

 born before its time. It has been buried and res- 

 urrected several times throughout the century. De- 

 fended in Britain by Thomson, scouted by Berzelius, 

 revived by Dumas, it was once more sent to rest 

 about 1860 by Stas, a Belgian chemist, who did 

 splendidly accurate work, from 1860 onwards, in 



