[226 J 



terbid, prcfently after the heat was applied. This wa& 

 the cafe with whatever degree of heat the charcoaL had: 

 been made. I f, however, the charcoal had not been made 

 with a very considerable degree of heat, there never failed 

 to be a permanent addition of inflammable air pro- 

 duced i which agrees with what I obferved before, 

 that, in converting dry wood into charcoal, the greater!: 

 part is changed into inflammable air. I have fome- 

 times found, that charcoal which was made with the 

 moft intenfe heat of a fmith's fire, which vitrified; 

 part of a common crucible in which the charcoal was 

 confined, and which had been continued above half 

 an hour, did not diminish the air in which the focus 

 of a burning mirror was thrown upon it ;. a quantity 

 of inflammable air equal to the diminution of the- 

 common air being generated in the procefs j whereas, 

 at other times, I have not perceived that there was 

 any generation of inflammable air, but a perfect 

 diminution of common air, when the charcoal had. 

 been made with a much lefs degree of heat. This 

 iubject deferves to be farther inveftigated. 



To make the preceding experiment with ftill more 

 accuracy, I repeated it in quickfilver j when I perceived 

 that there was a fmall increafe of the quantity of air, . 

 from a generation either of fixed or inflammable air,. 

 but I fuppofe of the former. Thus it flood without 

 any alteration a whole night, and part of the following 

 day j when lime-water, being admitted to it, it pre- 

 fently became turbid, and> after fome time, the 

 whole quantity of air, which was about four ounce 

 meafures, was diminiihed one fifth, as before.. In 

 this eafe, I carefully weighed the piece of charcoal, . 

 which was exactly two grains, and could not find 



that 



