2t}2 Messrs. Allen and Pepys on the 
been influenced by it ; so that if no chance of error had existed 
in estimating the carbonic acid gas from the residuum after 
barytic water had absorbed a part, still the result would not 
have been satisfactory. 
The experiments which we have had the honour of laying 
before this Society prove several important points : 
ist. That the estimate given by Lavoisier, of 2S parts of 
carbon in every 100 parts of carbonic acid, is very nearly cor- 
rect; the mean of our experiments makes it 28,60. 
edly. That the diamond is pure carbon ; for had it contained 
any notable proportion of hydrogene, it must have been dis- 
covered, either by detonating with the oxygene, as in the case 
of animal charcoal, or by diminishing the quantity of oxygene 
gas. 
gdly. That well burnt charcoal contains no sensible quantity 
of hydrogene ; but if exposed to the air for a few hours it 
absorbs moisture, which renders the results uncertain. 
4thly. That charcoal can no longer be considered as an 
oxide of carbon, because, when properly prepared, it requires 
quite as much oxygene for its combustion as the diamond. 
This is also the case with stone coal and plumbago. 
5thly. It appears that diamond and all carbonaceous sub- 
stances ( as far as our present methods of analysis are capable 
of demonstrating their nature) differ principally from each 
other in the state of aggregation of their particles. Berthollet 
has well remarked, that in proportion as this is stronger, de- 
composition is more difficult: and hence the variety of tempe- 
ratures required for the combustion of different inflammable 
substances. 
