242 Improvement of Forest Plantations. 
Mr Withers, previously to publishing the last of the above works, had 
addressed me, among others of his correspondents; and he subsequently 
did me the honour to publish the answer that I returned him, and which 
I take the liberty of extracting from the 90th page of his Letter to Sir 
Henry Stewart. I am not vain enough to imagine that my reply was 
entirely conclusive and satisfactory, but such as it is, it may convince 
the philosophic enquirer how much depends upon the energy excited by 
the great natural agents, and how little the planter is entitled to expect 
success, who does his work in a slovenly manner, and neglects to place 
his trees in situations where they may be duly exposed to the influence 
of those elements which Nature is ever ready to employ in completing 
the due development of her own perfect works. Without further pre- 
face I now extract the Letter that I have alluded to. 
"In replying to your enquiry, 'whether I conceive the application of 
manure to poor land at the time of planting, can have any injurious 
effect upon the quality of the timber ?' I must observe that many writers, 
chiefly, I believe, of the Scotch school, are of opinion, that to interfere 
with the growth of forest trees is but to injure them: thus, I read in 
the third volume of the Library of Entertaining Knowledge, part f, 
p. 166, ' the wood of these two genera, fPrunus and Mespilus,J is 
close and com[)act, and takes a good polish ; that of the wild sorts being 
better than the cultivated, and the deterioration being in proportion to 
the highness of the cultivation. In this, they follow the general law, 
that self-planted trees yield the best timber, &c.' But these assertions 
are of little weight with me, who know that men can believe and assert 
anything. 
"I believe that manure is of vast and essential utility to forest, as well 
as to garden trees, and that, for the following reasons. On another occa- 
sion, (Gardener's Manual, p. 16, No. 21,) I have observed that 'the 
pure earths alone do not perform any material part in the process of 
vegetable nutrition ; they may be considered as the media by which the 
plant is supported, and through which, it is enabled to supply itself with 
the aliment necessary to the growth and development of its parts. 
This aliment appears to be furnished either by decayed vegetation, 
naturally, {i. e. by absorption of the products of natural fermentation, 
either from the surface of the ground, or floating in the atmosphere,) or 
artificially and chiefly, by the organic materials applied by labour. 
Vegetables are found to be resolvable into the elements, carbon, oxygen, 
and hydrogen. Hence, they must require for their food such substances 
as are capable of producing the like elements. 
"Now, as the native earths are chiefly metallic oxides, it follows of 
necessity, that plants are nourished either by water alone, and therefore 
that vnfcr is t!ie origin of all hyd:o-carbonous bases; or, that vegetable 
and auiiuai manures are the sources from v;hich trees and plants most 
readily derive their nourishment. I believe, indeed, that plants are na- 
