HISTORY OF THE ATOMIC THEORY. 1 ^ \ 



ments and observations"* of Dr. Higgins. In distilling 

 acetate of lead, he found a certain amount of what he calls 

 acid matter in the fixable air, which he considers, as before 

 mentioned, to be a peculiar principle. It combines with the 

 empyreal air (oxygen) of the litharge. Not accounting for 

 the whole amount by the measurements he made, he inferred 

 " that when the acid matter of acetous acid is employed in 

 excessive quantity to form fixable air with the empyreal air 

 of litharge, the fixable air may consist of a little more than 

 one part of the acid matter, combined with two of the empyreal 

 air. By a more accurate estimate of the fixable air taken at 

 85 grains, it is most probable that the proportions would be 

 found ft be accurately two to one, provided fixable air, like 

 other acids, may not subsist with various proportions of the 

 empyreal air." t 



He mentions the definite proportion, two to one, because 

 he obtains the figures approximatively so, but he not only 

 fails to elevate it into a principle, but speaks of various pro- 

 portions as probable in the case in hand, and as usual in other 

 cases. This seems equal to saying distinctly that he recognised 

 no such principle. But does the term ** various proportions" 

 allude to fixed numbers, such as two or three ? There is no 

 reason to suppose this, he uses the word in the ordinary sense 

 it was then used, no other sense had been given to it, and 

 any other sense in this place is impossible. 



When firing with oxygen the inflammable gases from 

 acetate of lime, he says, in reference to some experiments 

 unnecessary to be detailed, *' by other experiments and the 

 same kind of estimation, the empyreal air appeared to con- 

 stitute more than two-thirds of the fixable air, and in some it 

 seemed to be accurately two-thirds ; but after all I continued 



* Experiments and observations relating to acetous acid, fixable air, dense 

 inflammable air, oils and fuel. The matter of fire and light, metallic reduction, 

 combustion, fermentation, putrefaction, respiration, and other subjects of 

 chemical philotophy. By Bryan Higgins, M.D. London, 1786. 



t Pago 23-2. 



