on the Combujtion of the Diamond. 185 
to air, becomes there, in a certain degree, incombuftible, as 
is proved in the experiment made by Mr. Tennant, which I 
have mentioned in the article Air in the Di@ionnaire de 
Chemie Encyclopedique, Vol. 1. p. 724. 
The anfwer to all thefe queftions may be found in the 
theory I have laid down: they are charcoals in the firft de- 
eree of oxydation. Thus fome of them have not yet acquired 
that which conftitutes charcoal properly fo called; others, 
after poffeffing all the qualities of vegetable and mineral car- 
bon, have returned to the firft degree by a real (debrulement) 
unburning of the remaining carbon; {fo that by lofing their 
imflammability they become capable of fixing a greater quan= 
tity of oxygen, and confequently of fetting at liberty a greater 
quantity of caloric when they find themfelves at a tempera- 
ture fufficiently high to determine and complete their acidi+ 
fication. 
Some practical confequences will doubtlefs hence be de- 
duced in regard to procefies for the reduCtion of ritetals; for the 
cementation of fteel, which it is probable takes up only oxyd 
of carbon, fince it is feparated from it in that ftate; for the 
incineration of the carbonaceous refiduums of our analyfes ; 
for the carbonifation of wood, pit-coal, and turf: in a word, 
we may perhaps thence conclude the poflibility of rendering 
ufeful thofe mafles of pit-coal, faid to be incombuttible, found 
at Rive-de-Gier, by mixing it with more inflammable mat- 
ters, to maintain the temperature which determines its com- 
buftion. Its pofition, texture, afd all its exterior characters 
announce, as already faid, that it confifts of beds of coal 
changed by a fubterranean fire; and this is confirmed by 
tradition, which preferved to that mountain, for three cen- 
turies, the name of the Mozntain of Fire. (Montagne de 
Feu.) We can now pronounce that it 1s coke too far ad- 
vanced, but fo much the more fufceptible of producing a 
great heat under favourable circumftances. 
i _ RECAPITULATION. 
I fhall here enumerate the confequences, or rather the 
fa&ts, which refult from the phenomena obferved in the two 
Vou.V. Bb ~ combui- 
