70 
THE CULTIVATOR. 
How came the rocks in this form? The rocks 
Came in this form mainly through the influence of 
$,ir, frost, water and acids. We, by a little observation, 
can see and understand how powerful an agent water 
is in breaking down rocks and depositing them in the 
form of soil. We need but visit any of the thousand 
|ittle streams that come babbling from the hills, 
through as many rocky ravines. By tracing any one 
of the busy rivulets to its source, and noting all of 
the materials over which it flows, and gathering a 
specimen of each, then descending to the plains, 
where it more leisurely glides, where the materials 
which it has gathered in its course among the hills 
are deposited—at first the more coarse, then the 
more fine—we shall find that the samples gathered 
correspond in almost every respect, except in that of 
fineness, with those which have been brought down 
from the highlands by the stream, and left on the 
plain in the form of soil. 
This is what we observe on a small scale. The 
larger streams, as well as the smaller, are engaged 
in the same work of wearing down in one place and 
depositing in another. Water, holding in solution 
sifCids,—as carbonic, sulphuric and nitric,—exercise 
an action in decomposing the rocks with which they 
Come in contact; but this action is chemical, not me¬ 
chanical, and very limited too, when compared with 
that of the busy rivulet, the ever plodding river, the 
surf-beating lake, or the storm-driven ocean. Frost 
and atmospheric changes, also, exercise a powerful 
influence. It is through the action of these agents, 
that the soils are formed, fitted and sustained, so as 
to support vegetation in such abundance and luxury. 
Some soils are made up almost entirely of one 
kind of rock. When this is the case, it is evidence 
that the soil has not been transported from any other 
place, but that it has been formed mainly by the de¬ 
composition of the rock on which it rests. This oc¬ 
curs in many places where there is no drift or trans¬ 
ported materials, and the same rock extends over a 
considerable range of country. 
The advantage of knowing the composition of the 
rock on which such a soil rests, is, that by knowing 
it, we know the general composition of the soil. 
Soils are often made up of the worn down fragments 
of a number, and sometimes of a great variety of 
rocks and simple minerals mixed together. A soil of 
this description is generally drift, i. e , has been 
transported from a distance, unless it occurs where 
a number of rocks crop out in the same vicinity. 
By knowing the composition of the various rocks 
which compose this soil, the composition of the soil 
can be approximately determined or arrived at; in 
other words, we have a general idea of its consti¬ 
tuents. 
This knowledge could be very advantageously used 
in the purchase of lands, in selecting grain farms, 
grazing farms, or in deciding in a general way, upon 
the kind of crop or crops best suited to a soil, and 
Feb, 
what it would probably be necessary to add in order 
to fit it for any particular grain, root, fruit, &c. 
Other things being equal, the more completely the 
fragments of rock are broken down or divided, the 
more productive the soil which is formed. The 
reason of this is, the finer the particles, the more 
readily are they dissolved or separated into their 
proximate inorganic constituents. They must be 
dissolved before they can enter the plant as food. 
The advantages to be derived from knowing the 
precise composition of soils. —The knowledge which 
we derive from studying or knowing the composition 
of rocks, although very useful and important, is so, 
for the most part, only in a general way. It gives 
us a kind of information which we could gain by no 
other means, and may be considered as a stepping- 
stone to a series of inquiries or investigations, more 
special and minute, to wit: the study of the com¬ 
position of soils. 
One great aim of the agriculturist, should be to 
know the precise composition of the. soil he cultivates. 
If he knows this, he is able to calculate the actual 
and the percentage amounts of the several inorganic 
bodies and organic matter, which enter into the com¬ 
position of an acre or any given area of his land, at 
the depth of six, ten or twelve inches. This gives 
him the quantity of each ingredient of his soil which 
lies within reach of the plants he grows. The prac¬ 
tical utility of this knowledge, will be more plainly 
set forth when we come to speak of the advantages 
to be derived from knowing the composition of cul¬ 
tivated plants, and that of the substances used for 
manures. 
The practical utility of knowing the composition 
of cultivated plants. —It is not enough for him who 
tills the ground to know the constituents of his soils, 
and that of the rocks on which his soils rest. Every 
one who follows the pursuit of agriculture, who at¬ 
tempts to avail himself of the advantages which 
practical chemistry affords, finds that after he has 
obtained an analysis of his soil, and that of the 
rocks on which it rests, that although this informa¬ 
tion is of great practical use, yet there is still a 
something wanting in order to regulate and adjust 
the compass which is to guide him understanding^ 
and safely on. He says to himself, “ I understand 
what the ingredients are which compose my soil, 
but I do not know what my crops remove from it, as I 
am ignorant of the substances which compose them. 
If I did know what ingredients entered into the com¬ 
position of my several crops, and the percentage 
quantity of each ingredient, then I could calculate 
nearly the exact amount of each that is taken away 
from my ground, and could adopt measures to re¬ 
turn them as fast as removed.” 
The advantages to be derived from knowing the 
composition of manures. —Suppose, now, that he 
knows the composition of his soil, rocks and the 
plants he cultivates; he still feels that there is yet 
