96 IrhU 
The loss of weight in charring wood is inconceivably 
great. In the large way it is almost impossible to ascer- 
tain it to any degree of exactness. The qualities of wood 
are so various, and the tendency which some have beyond 
others of parting with their juices, even when exposed to 
the same temperature, render it at best but a matter of -un- 
certainty * I shall however insert a few which I have char- 
red in the small way, and the results obtained from them ; 
before weighing they were all exposed to the same tempo* 
rature for a considerable time, and thoroughly driedo 
It is however worthy of remark, that the produce in 
chafeoal in the small way, does not give an invariable 
standard whereby to judge of that obtained on a large 
scale, where ignition is caused by the admission of extern 
nal air into contact with the wood. In the large way the 
quantity of char afforded will depend more upon the hard* 
ness and compactness of the texture of wood, and the skill 
of the workman, than on the quantity of carbon it contains* 
In the following tables I have simply expressed the ex* 
istence of the alkaline principle, in the various ashes ob* 
tained from the combustion of i pound of wood avoirdu- 
pois weight : this may be of use to those who wish to 
make experiments upon the formation of pot-ash. It 
will also be observed, that there are some woods that yield 
a much larger proportion of carbon than oak : these, 
however, are either too scarce or two valuable to be appli- 
ed to the manufacturing of iron in this country. 
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