S88 Proceedings of Philosophical Societies, [Mat^ 



a stove. Count Romford obtained this singular cpnclusion, that 

 the specific gravity of the solid matter which constitutes the 

 iimhei- of wood is almost the same in all trees. By the same 

 means he deteriDioed that the woody part of oak in full vegeta- 

 tion is only four-tenths of the whole. Air constitutes one-fourtii 

 of its and the rest consists in sap. Light woods have still a 

 much less quantity of solid matter ; but the season of the yeaij 

 and the age of the tree, occasion considerable variations. Ordi- 

 nary dry wood contains above one-fourth of its weight of water. 

 Even the oldest wood, though in the state of timber for ages, 

 never contains less than one-sixth of its weight of v^/atcr. 



Count Romford has determined, by exact experiments, that 

 all absolutely dry woods give from 42 to 43 per cent, of charcoal. 

 Hence he concludes that the ligneous matter is identic in all 

 woods. This loss, which the driest wood experiences v/heri 

 charred, the absolute qoaotity of carbon determined by Thenard 

 and Gay-Lussac at 52 or 53 per cent., the matters which are 

 deposited on the vessels, and finally tliis fact that wood too 

 •much dried, too nearly approaching to the state of charcoal, gives 

 out less heat — all these circunistances induce Count Rumford to 

 believe that the proper charry fibre^ which he calls the woody 

 skeleton, is surrounded by another substance, which he com- 

 pares to tlie muscles, and which he calls vegetable flesh. The 

 lire first attacks this envelope, because it contains hydrogen, 

 which renders it more infiaminable, and which contributes a 

 great deal to the heat given out by wood. 



From numerous experiments and complicated calculations^ 

 Count Rumford has drawn up a table of the quantity of water 

 whicli the different woods, according to their state of dryness^ 

 can heat from the freezing to the boiling temperature. From 

 this table it appears that the lime-tree gives out the most heat ^ 

 and the oak the Ieast_,, during combustion. From the same 

 analyses it follows that the inevitable loss of heat during the 

 charriog of wood is more than 42 per cent,, and by the ordinary 

 processes of the charcoal-makers more than 64 per cent., be- 

 cause they form a considerable quantity of pyrolignous acid, 

 which consumes this great proportion of carbon. It follows, 

 likewise, that all the charcoal furnished by any wood whatever, 

 furnishes only one third of the heat that is furnished by the wood 

 itself from which it was formed. 



Count Rumford conceives, likewise^ that lie has ascertained 

 this importarit fact for chemistry^ that carbon may combine with 

 oxygen, and form^with it carbonic acid^ at a much lower tern" 

 perature than that in winch it burns visibly. 



The difficulty of following this philosopher in his compli- 

 cated calculations respecting the greatest intensity of heat which 

 it it possible to produce, and on the quantity of heat evolved by 



