102 
STRUCTURE OF WOOD, &C. 
various 3 kinds ^ ass covers * heat was managed with great care, in 
of wood. order to determine with precision, from the weight of the vases, 
the moment when the operation was finished 3 the experiment 
occupied four days, and as many nights. When the vases with 
their contents ceased to lose weight, the process was stopped, 
and the charcoal was weighed while still hot. 
The following were the results. 
C Poplar. . . . 43*57 parts. 
\ Lime 43*59 
100 parts in weight of dry wood, ) Fir 44‘1 8 
gave in dry charcoal. j Maple. . . . 42*23 
f Elm 43*27 
VOak 43 00 
The medium term of the results of these 6* experiments gives 
43*33 parts of charcoal in SOO parts of dry wood ; and as they 
were made with woods differing considerably in their apparent 
weight, their hardness, and other distinctive physical characters, 
We may conclude from the great similarity of the results of 
these experiments, that none of the circumstances, from which 
the woods derive their particular characters, have any material 
influence upon the quantities of charcoal they are capable of 
yielding 3 and hence we may deduce that the ligneous substance, 
or seer- wood, if not the same in all, is at least composed of 
indentical substances. 
There is still, however, a very interesting question remaining 
for discussion, v\%. Is the seer-wood, charcoal ? 
To elucidate this question, I began by examining whether 
charcoal had the same specific gravity as seer-wood. 
j, therefore, reduced some common oak charcoal, *which 
appeared to be well manufactured, into pieces about the size of 
small peas, and then boiled them in a pretty good quantity of 
Seine water, previously well filtered : the pores of the charcoal 
were speedily so completely filled with this liquid, that becom- 
ing heavier than the water, in equal bulk, it precipitated itself 
to the bottom of the vessel, and there remained. 
On removing the vessel from the fire, the water was suffered 
to cool to the temperature of 60° F. 3 and then the charcoal, 
y/hile still submersed, was put into the small glass vase of the 
hydrostatic 
