102 HISTORY OF CHEMISTRY. [LECTURE VI. 



was so extraordinarily serviceable that it rendered possible the 

 fixing of these most important numbers, so that alteration was 

 necessary in only a few cases. 



It will thus be understood how the system of Berzelius 

 became the prevailing one, and why his judgment was authori- 

 tative. The publication of his yearly reports (Jahresberi elite), 

 which began to appear in 1821 and were employed not merely 

 for reporting but also for criticising, contributed to increase his 

 influence. Hence the ideas of "others possess only a subordi- 

 nate interest, but still I wish to state the views of some of his 

 contemporaries, so that I may the better characterise the period 

 under review. 



British chemists had not yet come to a decision with re- 

 spect to Dalton's conception of the atom and Wollaston's of 

 the equivalent. Very little of much importance had mean- 

 while been accomplished in Great Britain. The only thing to 

 which I wish to refer is the hypothesis of Prout, which was the 

 occasion of much discussion. 



Prout, in 1815, thought it was possible to show that the 

 atomic weights of the gaseous elements are multiples, by whole 

 numbers, of that of hydrogen. 43 Stated in this way, the matter 

 seems to be of small importance ; but it gains interest from the 

 fact that, if it is admitted to be generally applicable, it almost 

 necessarily leads to the assumption of a primordial form of 

 matter, and to the view that the manifold peculiarities of sub- 

 stances are explicable by the varying distribution of this matter 

 in space. Thomson 44 set himself the task of extending the 

 statement of Prout to all the elements, and, for this purpose, 

 he carried out a large number of atomic weight determinations. 

 His results are worthless, however, as Berzelius somewhat bluntly 

 points out to him. 45 



At a later period, Prout's hypothesis was taken up again by 

 Dumas, 46 after it had been shown that a more accurate deter- 



43 Ann. Phil. 6, 321. ** Thomson, An Attempt to establish the 

 First Principles of Chemistry by Experiment, 2 vols. London (1825). 

 45 Berzelius, Jahresbericht 1823, 40. 46 Ann. Chim. [3] 55, 129. 



