BOYS DEPARTMENT. 
35 
Bogs' department. 
AGRICULTURAL CHEMISTRY.— No. 9. 
' Soils are divided and named according to their 
texture) that is, according to the ingredients of 
which they are composed. You are familiar with 
the terms clay, sand, and gravel, and know some- 
thing of the character of the soil to which these 
names are applied; and you may have read of cal- 
careous, argillaceous, and alluvial soils, without 
getting any very definite idea of their nature. The 
design of this letter will he to explain the general 
and chemical character of different soils, so that 
when you see or read of any of them hereafter you 
may know of what ingredients they are composed. 
Sandy Soils. — You are well acquainted with the 
appearance of sand, and are aware that, where it 
exists in considerable abundance, it forms what is 
called a sandy soil. Grains of sand are composed 
mostly of silica (a substance described in my last 
letter), united with a small portion of alumina 
(which will be described presently), and oxide of 
iron (oxygen and iron). When sand is combined 
with lime, or clay, so as to form solid masses, it is 
called sandstone, a substance frequently used for 
building purposes, and for making millstones and 
grindstones. Sandy soils contain from 60 to 90 
per cent, of sand. 
Gravelly Soils. — These are so called from the 
quantity of gravel, or stony particles they contain, 
and have no distinguishing chemical property. 
Those in which limestone pebbles abound, are most 
profitable on account of their capacity for retaining 
vegetable matter and fertilizing ingredients longer 
than any other species of gravelly soil. 
Clay or Argillaceous Soils. — Clay is a mixture of 
the earth called alumina with silica and oxide of iron. 
As alumina does not enter into the composition of 
any vegetable, I did not describe it among those in- 
gredients of the soil which are absorbed by the 
roots of plants ; but its presence in every soil, and 
the important office it performs in modifying their 
texture, are sufficient reasons why its nature should 
be well understood by the agricultural chemist. 
Alumina is composed of an elementary substance, 
or base, called aluminum, united with a portion of 
oxygen. It is one of the essential constituents of 
the salt called alum, from which its name is deriv- 
ed. I told you alumina w r as one of the earths. 
There are ten bodies which chemists designate as 
earths, all of them composed of metallic oxides, but 
only four of them, viz : alumina, silica, lime, and 
magnesia are of much importance. Alumina and 
silica are found most abundant in nature, and their 
union, when in contact with oxide of iron, and 
often potash, forms clay. The components of clay 
are not merely mingled together, as many suppose, 
but they are chemically combined, and can only be 
separated by chemical means. Clay does not seem 
to possess any of the features belonging to its in- 
gredients separately, nor can these ingredients be 
united by any known chemical process so as to 
form true clay, such as nature produces. The 
three or four ingredients of which clay is composed, 
are united in various proportions, the silica usually 
being the most abundant. Sometimes 100 parts of 
clay contain over 90 parts of silica, with variable 
proportions of potash. 
Calcareous Soils. — When lime predominates or 
exceeds 20 per cent., the soil is called calcareous. 
When a clay soil contains much lime, it is called 
calcareous clay, and when lime abounds in a soil 
otherwise sandy, it forms calcareous sand. 
Marly Soils. — These are also soils containing a 
large amount of lime, and sometimes, though not 
so much potash as those called calcareous. When 
the lime is over five, and under 20 per cent., it 
forms a marly soil. When sand and lime are the 
principal constituents, the soil is called a sandy 
marl; clay and lime abounding produce a clayey 
marl. Marl is often used to improve the texture of 
soils, and sometimes with much advantage. The 
presence of lime in any soil may be detected by 
testing it with muriatic (hydrochloric) acid. Effer- 
vescence takes place when lime is present. 
Loamy Soils. — Loam is a term very indefinitely 
used among agriculturists, though always designat- 
ing a good soil, and one containing considerable 
vegetable matter and clay. Professor Johnston 
calls those soils loamy which contain from 30 to 60 
per cent, of sand, the rest being clay, lime, potash, 
and vegetable matter. A loam, where clay pre- 
dominates, is called a clay loam, and one where sand 
is most abundant, a sandy loam. 
Alluvial Soils. — These are formed by the wash- 
ings and depositions of rivers, or streams. The in- 
gredients of such soils are determined by the cha- 
racter of the soils through which the streams pro- 
ducing them have flowed. They are always rich 
and productive, because they contain much animal 
matter, and as they have been forming perhaps for 
ages, those ingredients to which they owe their fer- 
tility, extend to a great depth, forming an almost in- 
exhaustible supply of nutritive matter for vegetation. 
Peaty Soils. — Peat is formed by the decomposi- 
tion and decay of vegetable matter in low and moist 
situations. The mud and various substances con- 
tained in the water, unite with the remains of 
mosses and such plants as grow in low grounds, 
and as the decay of the vegetable matter progresses, 
all of these substances become intermixed and 
amalgamate, until a black, compact, spongy mass is 
formed. This is peat, and where it abounds, it pro- 
duces what is called a peaty soil. Peat bears a close 
resemblance to humus, or vegetable mold, which 
I will describe in my next letter. J. McKinstry. 
Greenport, Columbia Co., Dec. 1st, 1848. 
The way Domestic Animals Collect their 
Food. — The horse, when feeding on natural herb- 
age, grasps the blades with his lips, by which it is 
conducted between the incisiors, or front teeth. 
These he employs for the double purpose of hold- 
ing and detaching the grass, the latter action being 
assisted by a twitch of the head. The ox uses the 
tongue to collect his food. That organ, being so 
directed as to encircle a small bundle of grass, 
which is placed by it between the incisor teeth, 
and an elastic pad opposite to them in the upper 
j aw — between these, the herbage is pressed and 
partly cut, its complete severance being effected by 
tearing. The sheep gathers his food in a similar 
manner as the horse, but is enabled to bring his 
cutting teeth much nearer to the roots of the plants, 
in consequence of the upper lip being partially 
cleft. For his upper lip is thin, and is susceptible 
of considerable mobility; while that of the ox is 
thick, hairless, with a very limited action. 
