A PKIZE ESSAY. 
15 
hold yet a great deal of insoluble coal of mould- 
They want salts, and something which wil make this 
inert, dead vegetable matter of the soil a ftive. The 
mould is active in proportion as it is more or less dis¬ 
solved by water. Mould consists of two parts ; one is 
dissolved, though only in a slight degree, by water; 
the other is not dissolved by water. Some substances, 
however, do render mould very easily dissolved by 
water. Hence, if you reflect a moment on these facts, 
it will be seen that mould itself, being valuable in 
proportion to the ease with which water dissolves it, 
that whatever substance so enables mould to dissolve, 
may be added to it, and thus increase its value. Now 
the things which do this are the alkalies, soda, potash, 
and ammonia. These principles being well settled, 
we may enter on the consideration of each different 
manure. They will be valuable in proportion to the 
quantity and kind of salts each contains, added to the 
power they may have of producing by their decay 
substances which make their mould soluble. Now 
this last property, that is, the property of producing 
a substance which makes mould soluble, depends 
wholly upon the nitrogen of the manure. This nitro¬ 
gen, in the process of decay, becomes volatile alkali 
or ammonia. The word ammonia will occur so often 
in the present discussion, that we should endeavor to 
fix some definite idea to it. You need not, reader, be 
acquainted with all its chemical properties. I suppose 
every man who will be likely to read these remarks, 
has smelled ammonia. It has been already said, that 
it.gives the peculiar pungent smell to the common 
smelling bottle. 
This is volatile ammonia. It is always formed 
when animal or vegetable bodies decay. 
It has been already said, and is now repeated, in 
order that it may never be forgotton, that ammonia is 
formed by the union of hydrogen and nitrogen. Hy¬ 
drogen and nitrogen, two airs, nitrogen forming four 
fifths of the air we breathe; let that be borne in mind^ 
