Manchester Memoirs, ]\^/. h. {\g\\), No. V^. 9 



now that there must be ver>' simple ratios between the 

 volumes occupied by different atoms in the gaseous 

 state. Many writers^- have assumed that Gay-Lussac, in 

 his memoir, defined the relation between his law and the 

 atomic theory, but, as a matter of fact, he ignored it. He 

 did not recognise the theory, and the subject was 

 neglected and came to nothing in France for years. At 

 length, in 1814, Ampere published a memoir/^ of which 

 the fundamental idea is that the molecules of different 

 gases under the same conditions have the same size, so 

 that equal volumes of different gases contain the same 

 number of molecules. In this memoir, the first outcome of 

 the modern atomic theory in France, Dalton is not men- 

 tioned. 



In Italy Amadeo Avogadro had forestalled Ampere 

 by three years.^* Under the stimulus of Dalton's specula- 

 tions, of which he had learnt through Thomson's " System 

 of Chemistry," ^^ he composed the memoir in which he 

 advanced and maintained his famous hypothesis, that 

 under the same conditions the molecules of different gases 

 occupy the same volume. This hypothesis, involving 

 as it did a distinct departure from Dalton's ideas, became 

 the fundamental dogma of molecular science only after 

 the lapse of fifty years. 



In Sweden J. J. Berzelius had been occupied for some 

 time in determining the composition of metallic salts, 

 when Wollaston's memoir reached him.^' Forthwith he set 



^" See, for instance, Clerk Maxwell, "Theory of Ileal," lotli ed., 

 p. 326. 



1' Ann. Ckim., vol. 90, pp. 43-86, 1814. 



1* Jour. Phys., vol. 73, pp. 58-76, 181 1. 



^* " In what follows, I shall make use of the exposition of Dalton's 

 ideas which Thomson has given us in his ' System of Chemistry,' " /oc. (it., 

 p. 62. 



i» Phil. Mag., vol. 41, p. 3, 1813. 



