STRUCTURE OF WOOD, &C. 
113 
No. 13 
- - 39*605lb. of water, heated 180° F. 
Combustion 
And in No. 14 
- - 40*658 
Do. 
of wood and 
of charcoal. 
Medium 
- - 40 *1315 
Do. 
In order accurately to ascertain how much water this wood 
contained, I dried thoroughly in the stove a parcel of shavings, 
which had been previously dried over the chafing dish, and 
found that it still retained 6*977 p er cent, of water. 
Therefore we may conclude, that lib. of this wood contains 
only 0 930231b. of seer-wood. 
Now, if 0’93023lb. of seer-wood will heat 4013151b. of 
water to 180° F., lib. of the same wood ought to heat 43*141 
lb. ; and I therefore take this quantity of water heated to 
180° F. as the standard of the heat developed in the combus- 
tion of lib. of wood perfectly dried. 
Many persons have endeavoured to account for the heat 
manifested in the combustion of wood, by attributing it alto- 
gether to the charcoal contained in the wood burned. 
This hypothesis we have now to examine. 
It has been seen, that 100 parts of the wood of the lime- 
tree, perfectly dried, yielded 43*59 parts of charcoal $ conse- 
quently lib. of this wood, thoroughly dried, can contain only 
G*4359lb. of charcoal. 
According to the results of Crawford’s experiments, which 
we have found to be very accurate, lib. of charcoal furnishes 
in its combustion only the necessary heat for raising 57'608lb. 
of water to 180° F. ; therefore the charcoal contained in lib. 
of dry lime-wood, equal to 0*4359lb. can furnish in its com- 
bustion no more heat than is necessary to raise 25*11 lib. of 
water to 180°; but as the experiment has given 431411b., 
there must certainly have been some other substance burned 
besides the charcoal, and which could have been none other 
than hydrogen. 
Before, we determine the quantity of hydrogen consumed, 
it is essential to ascertain how much heat has been furnished, 
not merely by the charcoal itself, but by the charcoal and the 
carbon contained in the wood - 3 for it is very certain, that all 
the carbon was burned, since no pyroligneous acid was formed. 
Yol.XXXV. — N o. 162 . I Recording 
