^yo Sir H. Davy's Experiments^ &c. 
afforded by the charcoal from vegetable substances exist in it 
in the state of earths and alkalies : and as the quantity of 
hydrogene varies according to the degree of heat to which 
charcoal has been exposed, it is almost useless to attempt to 
assign its proportion in any particular case, especially when 
the largest portion is so extremely minute. 
The nature of the chemical difference between the diamond 
and other carbonaceous substances may be demonstrated by 
another process, namely, igniting them in chlorine ; when 
common well burnt charcoal, or plumbago from Cumberland, 
is intensely ignited in chlorine, white fumes are immediately 
perceived in consequence of the production of muriatic acid 
gas by the hydrogene, which acid precipitates the aqueous 
vapour in the chlorine; but the diamond occasions no such 
effect. A small diamond, weighing .45 of a grain, was kept 
in a state of intense ignition by the great lens of the Floren- 
tine Museum for more than half an hour, but the gas suffered 
no change, and the diamond had undergone no diminution of 
weight, and was not altered in appearance. 
Charcoal, after being intensely ignited in chlorine, is not 
altered in its conducting power, or colour; and this circumstance 
is in favour of the opinion, that the minute quantity of hydro- 
gene is not the cause of the great difference between the 
physical properties of the diamond and charcoal. 
