112 FOOD OF PLANTS, AND HOW THEY TAKE IT. 
2d.—It was bad policy to apply manure to the wheat 
crop, because the best portions of the mass were generally 
dissipated into the air, lost to the owner, by means of the 
fermentation that occurred in the manure heaps that were 
piled up to wait all through the summer, until the proper 
season of applying to the wheat in the autumn. From ob¬ 
servations of the loss that thus ensued, and in consideration 
of the axiom above referred to, a few of the most intelligent 
farmers learned to apply their manure exclusively to the cattle 
crops, and to apply it fresh from the yards, in a partially de¬ 
composed state, instead of waiting until much of the most va¬ 
luable portions had escaped. Those also who looked further 
and observed the absorbing power of certain substances, and 
who also learned that this volatile ammonia which was wasted 
from the manure could be chemically fixed or rendered non¬ 
volatile, still continued to heap their manures, but at the same 
time to compost them with suitable materials, loam, sods, road 
scrapings, swamp muck, &,c. &c., and to apply gypsum to the 
mass, whenever they could detect ammonia escaping from it. 
Many also went so far as to erect sheds to protect the pile from 
the action of the weather, and to use pumps, by which the 
watery parts should be repeatedly thrown back upon the 
pile, to encourage the decomposition of the woody fibre it 
contained. For many crops the manure is thus brought 
into a much better condition, and by the fermentation a large 
proportion of the seeds of weeds would lose their vitality. 
Such a compost, half loam or peat, is thought better, load 
for load, than fresh yard manure. 
To recur to the main question, let me again refer to the 
great German philosopher, who has divided cultivated 
vegetables into four classes, according as one or other of the 
important inorganic elements predominates in their ashes. 
1st. Alkali plants .—Those which contain double alkaline 
salts, such as beets and potatoes—the vine. 
2d. Lime plants. —Those that contain the earths, especially 
lime and magnesia, as clover, peas, beans, &c. 
3d. Silexplants. —Those that contain silex, as the grasses. 
4th. Phosphorous plants. —Those that contain the phos¬ 
phates, such as wheat, corn, rye, oats, &c., the cereals—fruits. 
With these lights before us, and with the full understand¬ 
ing and adoption of the proposition that all manure is but 
food of plants, and that the stimuli of vegetation are heat, 
light, and perhaps electricity, with which latter upon the 
present occasion we need have nothing to do, we may hope 
to indicate a practice in the supply of plant-food, or manure, 
that will be productive of good results ; and as a summing 
up. the following propositions may be announced : 
