HISTORY OF THE ATOMIC THEOfiY. 249 



was his custom, even when his opinion changed; it was more 

 with a view of obtaining copies of his own works, than with 

 the view of continuing any law proved to be incorrect, as 

 appears from the preface to his Meteorology. 



In his " New System," Part Ist, he treats of heat and the 

 constitution of bodies ; in Part 2nd, which was published in 

 1810, he treats of the chemical elements. In these volumes 

 it is remarkable how thoroughly every idea has been revolved 

 in his own mind, and become his own, before he has ventured 

 to write it. Every chapter shows a strict independent thought, 

 but, on the other hand, the book is wanting in the results of 

 others, and could never consequently be a complete system. 

 He endeavours to construct the whole science himself, more 

 than could be accomplished by any man. The book is written 

 in a more attractive manner than systems of chemistry now 

 assume ; and there is a constant discussion of questions which 

 give an insight into the state of knowledge of the time and 

 the tendency of chemistry. Still ^e arrangement was not 

 well adapted for the young student, although the work was 

 a great fund of thought for the advanced man of science. 

 Even now few will be able to read it without advantage. 



Part 2nd is principally taken up in determining the com- 

 position of bodies and their atomic weights. In the appendix 

 he enters into discussion with Gay Lussac. He there says. 

 Gay Lussac's "opinion is founded upon a hypothesis that all 

 elastic fluids combine in equal measures, or in measures that 

 have some simple relation one to another, as 1 to 2, 1 to 3, 

 2 to 3, &c. ; in fact, his notion of measures is analogous to 

 mine of atoms; and if it could be proved that all elastic 

 fluids have the same number of atoms in the same volume, 

 or numbers that are as 1, 2, 3, &c., the two hypotheses would 

 be the same, except that mine is universal, and his applies 

 only to elastic fluids. Gay Lussac could not see that a 

 similar hypothesis had been entertained by me and abandoned 

 as untenable." In this he refers to the following in p. 188 of 

 2K 



