STRUCTURE OP WOOD, &C, 
105 
It has been shewn that 100 parts of an oak felled on the 6th of 
of September, while in a growing state, contained only 62 56 obtained from 
parts of seer wood, and that consequently 100 parts of such Vt °od. 
wood would yield only 2 69 parts of charcoal. 
In making these calculations, no account has been taken of 
the quantity of wood, or other combustible, burnt in orfer to 
heat the closed vessel in which the wood was carbonised, 
pursuant to the process here adopted. But it may be remarked, 
that such quantity will be increased or diminished according to 
the construction of the furnace, and the arrangement of the 
other parts of the apparatus ,* and it will always, be too consider- 
able to be omitted in the list of expences. 
As M. Proust obtained only 1 9 or 20 parts of charcoal in 100 
of oak, it is probable that some waste occurred in the process 5 
but as it is certain, that in the carbonisation of wood, some loss 
will happen ; so in the ordinary method of making charcoal, 
there is always a considerable reduction of the quantity that 
ought lobe produced, arising from the quantity of wood con- 
sumed, either wholly or in part, to obtain heat sufficient to 
char the portion of wood that is reduced to a coal. 
Messrs. Gay Lussac and Thenard found from 52 to 53 parts Combustion of 
of carbon in 100 of seer-wood ; but 100 parts of seer-wood charcoal * 
yielded me only 43 parts of charcoal i this difference, however, 
it is easy to explain, as will be seen in the sequel. 
Section VII. 
Of the Quantities of Heat developed in the Combustion of 
different Species of Wood. 
Many persons have already endeavoured to determine the 
relative quantities of heat furnished by wood and charcoal in 
their combustion 5 but the results of their inquiries have not 
been satisfactory. Their apparatus has been too imperfect, not 
to leave vast incertitude in the conclusions drawn from their 
investigations. Indeed, the subject is so intricate in itself, that 
with the best instruments, the utmost care is requisite, lest, 
after much labour, the inquirer should be forced to content 
himself with approximations instead of accurate results and 
valuations strictly determined. 
All woods contain much moisture, even when apparently 
very 
