116 
STRUCTURE OF WOOD, &C. 
< ombustion As the combustion of lib. of charcoal, perfectly dry, yields 
of wood and heat sufficient to boil56 608lb. of water, at the thawing tem- 
of cuarcoal, , , „ , , , , _ ° , 
perature 5 and as lib. of wood, thoroughly dry, furnishes 
43*33lb. of dry charcoal, it follows, that the charcoal produced 
from lib. of dry wood, should furnish in its combustion heat 
sufficient to boil 24 958lb. of water, at the thawing tempera- 
ture. 
But we have already seen, that the combustion of lib. of 
wood, thoroughly dry, should furnish sufficient heat to boil 
43*143lb. of water at the freezing temperature or, which is 
the same thing, to raise it to 180° of Fahrenheit’s thermo- 
meter. 
These two numbers (43*143 and 24*954) which express 
the quantities of heat in question, being in the proportion 
of 100 to 57*849, it is evidenr, that the loss of heat inevitable 
in the carbonisation of wood, is upwards of 42 per cent., or 
exactly 42* 151 per cent, of the total quantity that the wood 
will furnish. 
In order to determine the loss of heat which occurs in the 
forests, by the ordinary process of the charcoal-burner, it is 
requisite to ascertain the precise product of charcoal from a 
given quantity of wood, though it is probable that this product 
is very variable. M. Proust estimates it at 20 per cent, in weight 
at the highest. 
Adopting, for a moment, this estimate, and supposing the 
carbonised wood in the same state of dryness as what is usually 
sold for fire-wood ; as lOOlb. of such wood contains only 
0761b. of perfectly dry wood, this quantity would furnish 
in its combustion only the degree of heat necessary to raise 
32 043lb. of water to 180° F. 
But the 0*20lb. of charcoal produced by the carbonisation 
of lib. of this wood, according to the usual process, can only 
furnish by combustion a sufficient quantity of heat to raise 
1 1 *521 lb. of water to 180° F. ; and as the numbers 32 043 
and 1 1*521 are nearly in the proportion of 100 to 36, it should 
seem, that the loss of heat in question is about 64 percent. 
One very important fact, which appears to be well ascer- 
tained by the results of this inquiry, is, that all the charcoal 
produced from the carbonisation of 3lb. of aoy kind of wood, 
scarcely 
