16 
so as to be applied to the purposes of life. The 
different parts of the atmosphere are mingled 
together by winds or changes of temperature, and 
successively brought in contact with the surface 
of the earth, so as to exert their fertilizing influ- 
ence. The modifications of the soil, and the ap- 
plication of manures, are placed within the power 
of man, as if for the purpose of awakening his 
industry, and of calling forth his powers. 
The theory of the general operation of the more 
compound manures, maybe rendered very obvious 
by simple chemical principles; but there is still 
much to be discovered, with regard to the best 
methods of rendering animal and vegetable sub- 
stances soluble ; with respect to the processes of 
decomposition, how they may be accelerated or 
retarded, and the means of producing the greatest 
effects from the materials employed: these subjects 
will be attended to in the Lecture on Manures. 
Plants are found by analysis to consist princi- 
pally of charcoal and aeriform matter. They give 
out by distillation volatile compounds, the elements 
of which are pure air, inflammable air, coally 
matter, and azote, or that elastic substance which 
forms a great part of the atmosphere, and which 
is incapable of supporting combustion. These 
elements they gain, either by their leaves from the 
air, or by their roots from the soil. All manures 
from organized substances contain the principles 
of vegetable matter, which during putrefaction are 
rendered either soluble in water or aeriform — 
and in these states, they are capable of being assi- 
milated to the vegetable organs. No one principle 
