HISTORY OF THE ATOMIC THEORY. 43 



to the last mentioned memoir, this letter alludes to his inves- 

 tigations generally, which had been everywhere discussed. 



On November 12th, 1802, he read to the Literary and 

 Philosophical Society an " Experimental inquiry into the 

 proportion of the several gases or elastic fluids constituting 

 the atmosphere."* 



These he made by weight, p. 257. 



Azotic gas 75.55 



Oxygenous gas 23.32 



Aqueous vapour 1.03 



Carbonic acid gas 10 



100.00 



In another place we find, by bulk 79 azote. 



21 oxygen. 



In describing his Eudiometric process he has a few observa- 

 tions of great importance, indications of the direction in which 

 he was moving, but given in such a way as to lead us to the con- 

 clusion that he had not yet seen their value; teaching us 

 also that an idea of definite proportions may exist without 

 any distinct nature of the completeness of the law of equiva- 

 lents as it stands. At page 249 he says, — 



"2. If 100 measures of common air be put to 36 of pure 

 nitrous gas in a tube 3-lOths of an inch wide and 5 inches 

 long, after a few minutes the whole will be reduced to 79 

 or 80 measures, and exhibit no signs of either oxygenous or 

 nitrous gas. 



"3. If 100 measures of common air be admitted to 72 of 

 nitrous gas in a wide vessel over water, such as to form a thin 

 stratum of air, and an immediate momentary agitation be used, 

 there will, as before, be found 79 or 80 measures of pure azotic 

 gas for a residuum. 



" 4. If in the last experiment, less than 72 measures of 

 nitrous gas be used, there will be a residuum containing oxy- 



* Ist vol. of Memoirs, new series, p. 244. 



