THE SOU THERN CULTIVATOR. 
101 
From iheAmerican Agriculturist. 
Necessity of a Knowledge of Chemical 
Principles to a Parmer, 
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It will be my object, ia the few brief remarks 
I intend to make in this paper, to illustrate, by 
some familiar examples, the absolute necessity 
of a knowledge of the principles of chemistry, 
to every one who expects to carry on the opera- 
tions 01 the farm, or even domestic affairs suc- 
cessfully. 
ffeai is one of the great agents of nature in 
effecting herchanges and modifying her res ults. 
What heat is, whether matter, or some effect or 
result of matter, is yet unknown. Great heat 
is always attended with light, and it is probable 
that, in all its degrees, it is inseparable from 
elec.ricity, and perhaps is identical with it. 
But it is my present object simply to show, by 
some practicable examples of every day occur- 
rence, some of the laws by which it acts. 
Heat expands, with some slight exceptions, 
all the objects into which it enters. Thus, a 
cold hand is shrivelled; but warmed, it is more 
plump and full. Every one knows that a boot 
or shoe that is too tight for summer use, can be 
comfortably worn in the cold of winter. An 
ordinary metallic pendulum that keeps correct 
time in summer, by its contraction, will beat 
too quick, and consequently produce fast time 
in winter, An iron bolt, when fastened while 
hot, will contiact on becoming cold, and close 
up a seam, which the power of man with 
the lever and screw, could not effect. The 
blacksmith sets his iron on the wagon wheels 
while red hot, and immediately cooling it, 
he sinks it sometimes half an inch on every 
side in the wood. The common Ihermorneter 
is another illustration of this principle. 
Fluids partake largely of this expansibility 
by heat. But its effects are more strikingly il- 
lustrated in air or gases, than in any other sub- 
stances. The particles of matter of which 
these are composed, are more easily separated 
and kept asunder, and they feel the influence of 
heat in a wonderful degree. A cubic inch of 
water when converted into steam occupies 1700 
times its original space, even when nearly of 
the same temperature. The principle on which 
all steam engines are propelled, is solely that of 
the expansive power of water and vapor by the 
application of heat. Thus, the heat yielded 
by a handful of wood, passing through a hall 
inch boiler into water, and then expanded into 
steam, will produce an effect that the combined 
strength of 100 horses could not accomplish. 
Hear produces nearly all the changes of wea- 
ther, by the rarefaction (or expansion)'of the 
air, and the consequent currents of that fluid 
which necessarily follow ; for as the heated air 
becomes necessarily lighter by expansion, and 
rises, heavier air rushes in, frequently from an 
immense distance, to supply its place, and hence 
storms and sometimes hurricanes, whose vio- 
lence is proportionate to their cause; and so if 
the air suddenly loses its heat, the neighboring 
warmer air harries to supply the partial va- 
cuum. 
Heat (another form of electricity perhaps, or 
in all cases associated with it,) is also the great 
agent of vegetable life, giving direction and ef- 
fect to the moisture and other elements of vege- 
tables, when the embryo plumules and cotyle- 
dons burst from the germ ; nor is its vivifying 
influence withheld for a moment from the grow- 
ing plant, till the entire reproduction is accom- 
plished, and the seed is fully matured which is 
to perpetuate other generations through the 
whole course of time. 
The most striking exceptions to the expan- 
sive effects of heat, are in clay, and water be- 
low a certain temperature. The former con- 
tracts through the highest known temperature 
that can be given to it; and a thermometer for 
furnaces, called, from the name of its inventor, 
Weagwood, has been constructed from this ma- 
terial, which is not injured by the most intense 
heat known. Water continues to contract till 
it reaches a temperature of 39® Farenheit, 
when, by a merciful exception to the general 
law, it begins to expand, and continues till it 
reaches 32®, the freezing point, when it con- 
geals. This keeps the cold water on the surface 
till it freezes, and this change of the liquid into 
a solid slill farther diminishes the densittq thus 
keeping the whole body of water in lakes and 
rivers beneath, in a condition to minister both 
support to its inhabitants, and allow the sur- 
plus water to pass off towards the ocean. 
The admission and retention of heat in bo- 
dies, is much affected by their substance and 
surface. A dense body will receive and retain 
more heat than such as are light and porous. 
A rough surface imbibes heat much quicker 
than a smooth one, when exposed to the rays of 
the sun or a fire ; and when at a higher tempe- 
rature than the surrounding atmosphere, parts 
with its surplus heat more readily than such as 
are smooth. The color of bodies has much to 
do with receiving and repelling heat, and re- 
taining or parting with it. A black surface, 
when exposed to a high temperature, soon be- 
comes hot, while such as are white, require a 
much longer time, under similar exposure, to 
reach the same temperature. Many substances 
of nearly equal density conduct heat with much 
greater facility than others. Let us consider, 
lor a moment, some beautiful examples of the 
application of these laws. 
Animals and birds inhabiting the arctic re- 
gions, where the cold is intense, are not only 
covered with thick fur and down, both of which 
are the best known conductors of heat, but on 
the approach of winter most of these change to 
a white color, which of all others is the worst 
conductor. During a great portion ofc an arctic 
winter, there is absolutely no sun. and for the 
remaining portion but a mere glimmering of 
its rays. All the warmth of living things in 
that region, therefore, is generated within the 
covering of fur or feathers, by the combination 
of the carbon of the blood derived from their 
food, and the oxygen of the air inhaled into the 
lungs, and all of which heat is most economical- 
ly husbanded for the comfort and preservation 
of the living being. 
The warm blooded animals that live in the 
Arctic ocean, w'hales, porpoises, seals, walrus- 
es, &c., are not less protected than those on 
land, though in a different manner. Fur orf'ea- 
thers, if constantly immersed ia water, would, 
after a time, admit it next the body, when a ra- 
pid lowering of its temperature would take 
place. Almighty wisdom has guarded the ani- 
mals which live in that element in a manner 
totally different, yet equally effectual with such 
as live in the air. They have a smooth, 
naked skin, or sometimes covered with a thin 
hair, which is no impediment to their rapid 
passage through the water; and underneath 
is a thick covering of fat, which, though vastly 
denser than fur or feathers, is nearly equal in 
its non-conducting properties. So, too, in our 
own climate, the hog, which is the only animal 
not sufficiently protected against the rigors of 
winter by an external covering, takes care to 
supply this deficiency effectually, if allowed to 
indulge his gormandizing propensities, by load- 
ing the exterior of his carcass, immediately un- 
der his skin, with a thick coating of fat. 
. The temperature of the human being has to 
be provided lor, through the extremes of winter 
and summer, by external clothing, though in ex- 
treme hot weather, a portion of this excessive 
heat is carried off by perspiration, which in- 
volves another beautiful principle of chemis- 
try, that we have not time at present to illus- 
trate. Black is the warmest clothing when ex- 
posed to the sun’s rays, and the coolest when 
deprived of them ; wAifc is directly the reverse. 
Consequently, there is no more unsuitable color 
for clothing, where temperature alone is regard- 
ed, either for winter or summer, than black, and 
none more proper than while. The effect of 
black is scniewhat obviated by using white li- 
nen and under-clothes. 
Black soils are more productive than such as 
are light colored, when in other respects they 
are equally charged with the elements of vege- 
table nutrition. They rapidly absorb heat when 
exposed to the rays of the sun, and as rapidly 
cool when they are withdrawn. Both of the.se 
effects are highly beneficial to vegetation. The 
heat which the soil acquires during the day, 
stimulates the action of the roots and growth of 
the plants; and the rapid cooling of the surface 
causes the dew with which the air is charged to 
be deposited early, and in large quantities, dur- 
ing the evening. Some gardeners use white 
sand on the top of the soils, “ because,” as they 
say, “ it is so heating.” Had they a knowledge 
of some of the first principles of chemistry, they 
would at once see the absurdity of the practice. 
Were the sand black, or of a dark color, the 
practice would be commendable, as it would 
conduct the rays to the roots of the plants, which 
its white color reflecls. The sand is highly use- 
ful when mixed with many soils, but is objec- 
tionable when placed on the surface. Pure 
sand is frequently hotter than dark earth in si- 
milar situations; but it is because it is drier 
and a non-conductor, and retains what heat is 
imparted to it, while the evaporation of the 
moisture, and heat-conducting properties of 
the dark soils, carry off the heat, A pure white 
or very light colored earth can never be fertile. 
Very luxuriant vegetables are always darlc co- 
lored when growing, and their color helps their 
growth in two ways — and for the same reason 
that dark soils do, viz: by conducting the heat 
into the plant w’hile the sun is up, and again 
conducting it off when down, by which there is 
a rapid and plentiful deposit of dew upon it. 
White buildings reflect the sun’s rays, while 
darker colors absorb them; consequently, those 
which are white are vastly more durable than 
such as are very dark. It would be more eco- 
nomical to use white for all buildings, fences, 
tools, &c,, used about a farm; even carts and 
sleighs and carriages would last much longer 
by substituting draborlight colors, lor the black 
or dark brown usually adopted. When black 
is used tor carriages, its bad effects are in a con- 
siderable degree prevented by the use of varnish, 
thus leaving a smooth polished surface, which 
reflects much of the heat. When not exposed 
to the direct rays of the sun. of course, there is 
no difference between this and other colors. 
The philosophy of placing plants that require 
much heat on the south side of white walls, is 
obvious. They reflect the rays of the son upon 
the plants and soil covering the roots, thus af- 
fording them a double supply of heat. The 
white exterior of the wall arrests and sends 
back the rays that fall upon it, precisely as the 
amalgam, or quicksilver, on the back of a look- 
ing glass arrests and sends back those which 
would otherwise be transmitted through it. A 
kettle or pot covered with soot, has the greatest 
advantage for absorbing heat, and when expo- 
sed to a fire. It will raise a liquid contained in it 
to the boiling point in hall the timetbata bright 
poli'^hed surface would, if similarly exposed ; 
and it will cool, when withdrawn from the fire, 
in equally less time. The blackened tea-kettle 
is, therefore, the proper vessel to heat the water, 
and the white porcelain, or highly burnished 
metallic tea-pot, the proper one to maintain it 
hot for the longest time. R. L. A. 
Buffalo, February, 1845. 
from the Genesee Farmer. 
Science with Practice# 
Every farmer should adopt lor his motto, 
“ Knowledge with Labor,” or, “Science with 
Practice.” Knowledge without labor, and labor 
without knowledge are alike nearly worthless. 
But knowledge with labor, or science with prac- 
tice, gives to the honest cultivator of the earth 
the best possible chance to acquire both wealth 
and distinction as a successful agriculturist. 
Suppose a farmer wishes to sow land enough 
this fall to yield him, at the least possible ex- 
pense, 500 bushels of good wheat, free alike 
irom rust, smut scaA chess — what knowledge does 
he need to accomplish this object? Will any 
experienced farmer say that, to produce this 
amount of grain at the least cost in land and 
labor, no knowledge of the mineral constitu^ 
