3 20 STRUCTURE OP WOOD, &C* 



but it undergoes no alteration of shape. This phenomenon is 

 easily accounted for : the water which distended the particles 

 of the clay, kept them at a distance from each other, and ren- 

 dered the mass soft and flexible, having been expelled by the 

 power of the heat, the several particles contract themselves 

 together, and form a hard and brittle body, though the clay 

 remains the same before and after the operation. 



Is it not possible that wo^d is converted into charcoal by a 

 similar process ? For, either the charcoal is already formed 

 in the wood, or the wood being decomposed, the charcoal is 

 formed of its elements, or a part of them. But is it not evi- 

 dently impossible that the elements of a solid body should be 

 so totally deranged as to separate tl em entirely from each 

 other without destroying the form or figure of the body ? 



In the sequel of this paper it will be shewn, that the specific 

 gravity of the solid parts of any kind of- wood is very nearly 

 the same as that of the charcoal obtained from it, a circum- 

 stance that gives a great degree of probability to the hypothe- 

 sis, that the two substances are identically the same. 



But I do not mean to amuse the Class with a detail of my 

 own conjectures ; it is to my experiments and their results that 

 I now claim the honour of calling its attention. 



I was by accident first induced to enter upon this examina- 

 tion and inquiry into the structure of wood. In the course 

 of a long series of researches upon heat, I wished to determine 

 the quantities of that element produced by the combustion of 

 different kinds of wood j but I had scarcely began the inquiry 

 when I found, that in order to procure satisfactory results to 

 my experiments, it was indispeusably necessary to obtain a 

 better knowledge of wood itself j and, therefore, I imme- 

 diately devoted myself to the study. 



My first aim was to determine the specific gravity of the 

 solid parts which compose the fabric of the wood, in order 

 afterwards to determine the quantities of sap or water contained 

 in wood under various circumstances. 



Having found, that very thin shavings filled with sap, or 

 even with water, could be thoroughly dried in less than an 

 hour, without injury to the wood, in a stove kept at a higher 

 temperature than that of boiling water, or at about 50° 



of 



