74 Mr. Davy’s Lecture on some new analytical Researches 
were covered with a grayish crust, and when acted upon by 
water and dried, were found to have lost about of a grain 
in weight. The matter separated by washing, and examined, 
appeared as a fine powder of a dense black colour. When a 
surface of platina wire was covered with it, and made to touch 
another wire in the Voltaic circuit, a brilliant spark with 
combustion occurred. It burnt, when heated to redness in a 
green glass tube filled with oxygene gas, and produced car- 
bonic acid by its combustion. 
These general results seem to shew, that in plumbago the 
carbonaceous element exists merely in combination with iron, 
and in a form which may be regarded as approaching to that 
of a metal in its nature, being conducting in a high degree, 
opaque, and possessing considerable lustre. 
Charcoal appears to contain a minute quantity of hydrogene 
in combination. Possibly likewise, the alkalies and earths pro- 
duced during its combustion, exist in it not fully combined 
with oxygene, and according to these ideas, it is a very com- 
pounded substance, though in the main it consists of the pure 
carbonaceous element. 
The experiments on the diamond render it extremely likely 
that it contains oxygene ; but the quantity must be exceedingly 
minute, though probably sufficient to render the compound 
non-conducting : and if the carbonaceous element in charcoal 
and the diamond be considered as united to still less foreign 
matter in quantity, than in plumbago, which contains about 
^ of iron, the results of their combustion, as examined inde- 
pendently of hygrometrical tests, will not differ perceptibly. 
Whoever considers the difference between iron and steel, in 
which there does not exist more than of plumbago, or the 
