So generally is the ligneous substance diffused through the vege- 

 table system, as to render it, perhaps, the most abundant of the 

 compound constituents of vegetables. It not only forms almost 

 the whole of the bulk of the trunks and boughs of trees, and shells 

 of fruits ; but it also forms a great part of the husks, and lanugi- 

 nous coverings of seeds, as well as of the epidermis of leaves, &c. 

 The quantity in which it exists agrees therefore in the abundance 

 of bitumen which seems to be yielded by that species of fermen- 

 tation, to which I have presumed that vegetables are subject; and 

 it is also worthy of notice, that the substances, which have been 

 just described, as containing a predominating proportion of the 

 ligneous part, are those substances which are most frequently found 

 in a bituminous or in a mineral state. 



The contemplation of nature teaches, that there exists a regular 

 system of dissolution and renovation, through all her works ; and 

 that there are certain laws, according to which, substances are forced 

 to quit one form of existence, and take on another ; their princi- 

 ples entering into new combinations, and forming other substances 

 equally necessary in the ceconomy of nature. Thus is constituted the 

 never-ending chain of varying existences, in which, though each 

 link differs from the rest, yet such is their symmetry and proportion, 

 that they form a whole, in which beauty and utility are eminently 

 conspicuous. But when we view the chemical history of the lig- 

 neous matter of vegetables, a link appears to be lost, and the chain 

 broken ; for whilst other substances yield either to the vinous, or 

 to putrid fermentation, the ligneous, we are told, seems to resist all 

 nature's efforts to force it into a new mode of existence. So re- 

 fractory does it appear, that it is esteemed the most insoluble and 

 unchangeable of all vegetable substances. If wood be exposed in 

 a close vessel to the destructive action of fire, so little of the lig- 

 neous substance is lost, that a charcoal is left which still retains 



VOL. I. FF 



