LAVOISIER. 239 



the heat applied was not very strong, though a stronger 

 heat dissipated the diamond altogether if exposed to the 

 air. Hence M. Lavoisier inferred, that beside being a 

 combustible substance, as Newton had sagaciously ima- 

 gined from its optical qualities, and as Macquer had 

 proved by direct experiment, it is capable of conversion 

 into charcoal. But a more important fact was also ascer- 

 tained. M. Lavoisier examined the air in which the 

 evaporation, as he terms it, of the diamond was per- 

 formed, and he found that it precipitated lime from lime 

 water. Examining the lime thus thrown down he found 

 it to be chalk, and thence concluded most justly that the 

 air produced during the combustion of the diamond was 

 fixed air. This, however, is not his enunciation of the 

 proposition; he only says, that the air in which the 

 diamond had been evaporated had acquired in part the 

 properties of fixed air, or the air which, he correctly 

 says, comes from the effervescence of alkalis and from 

 fermentation, and which, he very erroneously says, (fol- 

 lowing the mistake into which he had fallen in his expe- 

 riments on calcination) is the air given out by metallic 

 calces on their reduction to the reguline state. He rests 

 in doubt between the two inferences from his experi- 

 ments the one, that the diamond evaporates into fixed 

 air; the other, that its vapour changes atmospheric into 

 fixed air. 



Observing the analogy between the diamond and com- 

 bustible bodies, he exposed it to heat when surrounded 

 with fixed air, and atmospheric air was excluded. The 

 evaporation went on, but much more difficultly and slowly. 

 The probability is that the air was not entirely fixed air, 

 else the diamond could not have evaporated at all. 



