248 THE ATOMIC THEOET. 



not generalize. In some ways, doubtless, Dalton was narrow, and he 

 failed to recognize the improvements which other men soon intro- 

 duced into his system. The chemical symbols which he proposed were 

 soon supplanted b}^ the better formuhe invented by Berzelius, and his 

 views upon the densities of gases were set aside by the more exact 

 work of Gay Lussac, which Dalton never full}^ appreciated. As an 

 experimenter he was crude and excelled by several of his contempo- 

 raries; his tables of atoniic weights, or rather equivalents, were only 

 rough approximations to the true values. These defects, however, 

 are only spots upon the sun and in no wise diminish his glory. Dal- 

 ton transformed an art into science, and his influence upon chemistr}^ 

 was never greater than it is to-day. The truth of this statement will 

 appear when we trace, step by step, the development of chemical doc- 

 trine. The guiding clue, from first to last, is Dalton's atomic theor}-. 



Although Dalton tirst announced his theory in 1803, the publication 

 of his "systenr' in 1808 marks the culmination of his labors. The 

 memorable controvers}' between Proust and Berthollet had by this 

 time exhausted its force, and nearly all chemists were satislied that 

 the law of definite or constant proportions must be true. The idea of 

 multiple proportions was also easily accepted; and as for the combin- 

 ing numbers, they, after various revisions, came generall}" into use. 

 The atomic conception, however, made its way more slowi}^, for the 

 fear of metaphysics still governed many acute minds. Dav}' especially 

 was late in yielding to it, but in time even his conversion was efl:'ected. 

 Thomson, as we have already noted, was the earliest and most enthu- 

 siastic disciple of the new system, and WoUaston, although cautiously 

 preferring the term "equivalent" to that of atomic weight, made 

 useful contributions to the theory. These names mark the childhood 

 of the doctrine before its vigorous growth had thoroughly begun. 



The development of the atomic theory- followed two distinct lines, 

 the one chemical, the other physical, in dii-ection. On the chemical 

 side the leader was Berzelius, who began in 1811 the publication of his 

 colossal res;'arches upon definite proportions. At first he seems to 

 have been influenced b}^ Richter rather than by Dalton, but that bias 

 was only temporarj^ For more than thirty years Berzelius continued 

 these labors, inventing symbols, establishing formuhe, and determining 

 atomic weights. He, above all other men, made the atomic theory 

 applical)le to general use, a universal tool suited to practical purposes. 

 Turner, Penny, Erdmann, and others did noble work of the same 

 order, but Berzelius overshadowed them all. Throughout his long 

 career he was almost the dictator of chemistry. 



It was on the physical side, however, that the theory of Dalton was 

 most profoundly modified. First came the researches of Gay Lussac, 

 who, in 1808, showed that combination between gases always took 

 place in simple relations by volume, and also that all gaseous densities 

 were pro})ortional either to the com])ining weights of the several sub- 



