DECOMPOSITION OF WOOD, COAL, ETC. 365 



CHAPTER XII. 



ON THE MOULDERING OF BODIES. — PAPER, BROWN 

 COAL, AND MINERAL COAL. 



The decomposition of wood, woody fibre, and all 

 vegetable bodies when subjected to the action of 

 water, and excluded from the air, is termed mould- 

 ering. 



Wood, or brown coal and mineral coal, are the re- 

 mains of vegetables of a former world; their ap- 

 pearance and characters show, that they are products 

 of the processes of decomposition termed decay and 

 putrefaction. We can easily ascertain by analysis 

 the manner in which their constituents have been 

 changed, if we suppose the greater part of their bulk 

 to have been formed from woody fibre. 



But it is necessary, before we can obtain a distinct 

 idea of the manner in which coal is formed, to con- 

 sider a peculiar change which woody fibre suffers by 

 means of moisture, when partially or entirely ex- 

 cluded from the air. 



It is known, that when pure woody fibre, as linen, 

 for example, is placed in contact with water, con- 

 siderable heat is evolved, and the substance is 

 converted into a soft friable mass, which has lost 

 all coherence. This substance was employed in the 

 fabrication of paper before the use of chlorine, as an 

 agent for bleaching. The rags employed for this 

 purpose were placed in heaps, and it was observed, 

 that on their becoming warm a gas was disengaged, 

 and their weight diminished from 18 to 25 per cent. 



When sawdust moistened with water is placed in 

 a closed vessel, carbonic acid gas is evolved in the 

 same manner as when air is admitted. A true putre- 

 faction takes place, the wood assumes a white color, 

 loses its peculiar texture, and is converted into a 

 rotten friable matter. 

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