2Q0 Messrs. Allen and Pepys on the 
In two of our first experiments with box-wood charcoal, 
the calculations gave us in one case 29,75 parts of carbon in 
100 of carbonic acid, and in the other 30,68; but we were not 
then fully aware of the absorption of water by charcoal, which 
rendered the quantity of real carbon employed less than in- 
dicated by the weight. Also in another experiment, in which 4 
grains of diamond were consumed, the calculation gave us 29 96 
per cent, of diamond in carbonic acid ; but apprehending that 
a slight degree of inaccuracy had crept into this experiment, 
we have not detailed it with the rest ; but we have thought it 
right to give a simple statement of matters of fact ; in no one 
instance have we endeavoured to strain or accommodate these 
to suit any particular theory, being fully aware that every ex- 
periment, carefully made and faithfully recorded, will remain 
an immutable truth to the end of time, while hypotheses are 
constantly varying, and even the most beautiful theories are 
liable to change. 
The experiments above related give us the following results. 
By 
carbonic Acid. 
By Oxygene. 
Box-wood charcoal 
28,92 
28,77 
1st expt. diamond 
28,8l 
2d expt. diamond 
28,82 
28,72 
Stone coal 
28,20 
28,27 
Plumbago 
28,46 
28,4,6 
5 ) 
14 3 35 
5)H 3>°3 
mean 
28,67 
28,60 
Hence we conclude that 100 grains of carbonic acid contains 
28,60 of carbon, which does not greatly differ from the results 
of the experiments of Smithson Tennant, Esq. on the nature 
of diamond. See Phil. Trans. 1797. 
This gentleman made his experiment in the following 
