104 
STRUCTURE OF WOOD, &C. 
Quantity of by them (the beech and the oak) were composed of these 
C J ll 3 Tp njil ' ' * 
obtained from ^ ree elements in nearly equal proportions. They also dis- 
ivood. covered that the oxigen and hydrogen in these woods are in the 
requisite proportions for the formation of water : wherefore 
they concluded that carbon was the only combustible substance 
contained in wood. 
It will appear in the sequel, how well the results of these 
ingenious inquiries accord with those of my experiments. 
But first, I shall examine what quantity of charcoal it is 
possible to obtain from different species of woods, under 
various degrees of dryness, pursuing the method already adopt* 
ed in my experiments. 
From the mode in which charcoal is ordinarily made, a very 
considered portion is lost, and improvidently burned during 
the operation. 
As it appears to be clearly proved, by the results of the six 
experiments above related, that the quantity of charcoal to be 
obtained from any given quantity of wood, is invariably in pro- 
portion to the quantity of dry ligneous substance contained in 
the wood , the inquiry into the quantities of charcoal to be 
produced from different species of woods, at various degrees of 
dryness, becomes limited to that of the quantities of wood 
absolutely dry, contained in the woods in question. 
It has been shewn that 100 parts in weight of oak, thoroughly 
dried, gives 43 parts of charcoal. 
We have likewise seen, that 100 parts of oak as dry as it 
can be made in summer, at the temperature of 62° F. contains 
only 91 parts of seer- wood, and, consequently, that 100 parts of 
such wood would furnish only 39 13 parts of charcoal. 
From the results of an experiment, of which I have given an 
account in this memoir, it appears, that 100 parts of oak, in the 
state wherein it is found when exposed to the winter’s air, at 
the temperature of 4 6' F. contain only 83*36 parts of seer- 
wood ; consequently, 100 parts of such wood would yield no 
more than 35*84 parts of charcoal. 
From the examination we have made of the oak, in that state 
in which it is deemed fit for burning, we have found that 100 
parts of this kind of wood contain only 76 parts of absolutely 
dry wood j whence we conclude, that 100 parts of such wood 
would produce 32 68 parts of charcoal. 
It 
