VEGETABLE FIBRE. 151 



Though m the manufacture of paper, only fragments 

 which have been thoroughly rotted are made use of, yet 

 there will be found in the products the same kind of ine- 

 quality as to fineness, as in the manufacture of cloths : the 

 finest paper is made from linen rags, the coarsest from the 

 remnants of ropes. 



Charcoal consists almost entirely of the constituent prin- 

 ciples of vegetable fibre, from which the other elements 

 have been separated by the action of heat ; and as charcoal 

 forms the basis of vegetable fibre, I cannot well avoid speak- 

 ing of it in connexion with this subject ; and as it is an 

 article of such general use, it ought surely to find a place in 

 a work of this kind. 



The vegetables of which the combustion is the most in- 

 tense and lasting, are those which in their texture are 

 closest and driest : such give out less flame in burning than 

 others, but the heat is greater, and the superior quality of 

 the coals produced from them causes them to be preferred 

 for domestic heat, and for many of the operations of the arts. 



In some manufactures where it is necessary to apply heat 

 to bodies which collectively form a large mass, as in the 

 manufactories for porcelain and potter's ware, in lime-kilns, 

 &c., wood split fine and well dried is preferred, as it gives 

 out much flame, and leaves but a small residuum of 

 charcoal. 



Those plants in which the longitudinal fibres are disposed 

 in closely compacted bundles, possess all the qualities 

 necessary for combustion ; but the process is much less per- 

 fect in those which have not acquired this density, and are 

 still full of nutritive juices, than in those which have be- 

 come by age hardened into wood. 



Soil, exposure, climate, and season modify in a remarka- 

 ble manner the fibre of vegetables of the same kind. 



Vegetables raised in a dry and arid soil have a much hard- 

 er and more compact texture, than those of the same kind 

 raised in a moist and rich soil : they have more perfume, 

 contain a greater quantity of volatile oil, are decomposed 

 with more difficulty, and during combustion give out a 

 much more intense heat. Every one knows that thickets 

 having a southern exposure, yield better fuel than those 

 which lie towards the north ; the wood is more solid, and 

 after having been cut, it will resist for a longer time the 

 action of air and water. This fact was observed by Pliny, 

 in regard to the woods of the Apennines. 



