Inquiries relative to the Structure of Wood. 46 1 



inquiry, I can only recommend it to those whose inclina- 

 tions may lead that way. Leaving, therefore, this subject 

 untouched, I must, without any further circumerration, 

 pursue the original object I had in view in these disqui- 

 sitions upon wood, namely, to endeavour to become 

 acquainted with those inflammable substances which burn 

 on setting fire to a .piece of wood under a calorimeter. 



SECTION VI. Of the Quantities of Charcoal to be obtained 

 from different Kinds of Wood. 



Having discovered that pieces of wood, more or less 

 thick, may be perfectly carbonized in glass vases with 

 thin tops, closely covered, and exposed for two or three 

 days to a moderate heat in a stove, I adopted this 

 method in all my experiments on the carbonization of 

 wood. 



The glass vases which I make use of are what the 

 chemists call proofs, with feet : they are small cylindrical 

 vessels, about \\ inch in diameter and 6 inches in height; 

 the covers consist of glass plates about 2 inches in diam- 

 eter and from 2 to 3 lines in thickness, neatly ground 

 with very fine emery, well diluted with water, on a large 

 glass slab ; and, the edges of the vases being ground with 

 the same exactness, they become hermetically closed by 

 the covers, so as to preclude every access of the air, es- 

 pecially if the edges of the vases and the whole surface 

 of the covers be well rubbed with black-lead. 



The elastic fluids, in escaping from the interior of the 

 vases, occasionally raise the cover for a moment, on one 

 side, even when surmounted by a considerable weight ; 

 but as it is only raised a very little, and falls again im- 

 mediately, the vase is never open more than an instant 



