The republic. [volume] (Washington [D.C.]) 1849-1853, 1850-06-24
PATENT OFFICE REPoRT-PART IL.
CHAPTER iii.
AGRICULTURAL METEoRoLooY.

AGRICULTURAL METEoRoLooY.
There few sciences the study OF which il more
useful 10 the farmer than that Of Meteoroogy A
soil may contain all the atoms required to form
luxuriant crop, yet, il the temperature Of the
ground, OF the air above IL, be too low, vegeta
ton makes progress. Again, the earth and at
mospherc may have a due degree Of warmth and
light, well abound in all the food of plants in
an available FORM except toafer and the absence
of this element will be fatal TO the hopes of the hus
bandman.
Atmospheric air, light heat, electricity, rain,
dew, snow and frost, exert controlling influence
the growth Of all cultivated plants. A know
ledge Of the natural laws by which these generally
invisible and imponderable bodies governed, 50
far researches have revealed them, is alike vau-
able and interesting. The atmosphere and the nu-
merous phenomena of which it is the theatre, should
command more attention III this country than they
hitherto have received, II we intend TO keep pace
with the progress of physical science in Europe.
To encourage the study of meteorology in its appl
cation to agriculture is the object OF this chapter.
The ATMOSPHERE is mainly composed two dis
tinct gases, which are invisible but not impondcra-
bic bodies, and every where surround the planet
like an ocean. II has a mean depth of some forty
five mites. The gases which form the air called
nitrogen and Oxygen. According to the accurate
ANALYSIS OF dry. pure air, made by NM. Dumas
and Boussingault, 100 parts consist Of 20.S oxygen
and 1872 nitrogen. These chemists found from
to parts of carbonc acid in 900 of atmospheric
air Dr. Fresenius has asccrtaincd that the proper
ton OF ammonia in the atmosphere is to 2, 000,-
900, varying TO 10 !, 000, 900 Undoubtedly there
are many other volatile and gaseous bodies in the
atmosphere, in a state extremely diluted and diff
fused to escape all chemical tests Sir Robert
Kane found that sulphuretted hydrogen will pass
through thin piece OF India rubber into the at
mosphere, against a pressure equal to 90 times the
weight of common air Gaseous compounds Of
phosphorus, chlorine. and sulphur are constantly
discharged from decayng animal and vegetable
substances into the atmosphere These gases fall
to the earth again in rain water II ID one of the
laws peculiar to all gases, that the presence of one
in any given space does not in the least prevent
several others from occupying the vacancies left be-
tween atoms OF gas that seem to repci each other
with singular aversion. The facility with which
the atmosphere takes up vapor when water evapo
rates, Ia familiar to all.
This capacity To hold immense quantities of
imbbed from the ocean, lakes, rivers the foliage
Of trees and moist earth, IN a volatile condition. to
be distributed over broad continents, Id wonder.
ful provision of nature But the filling Of the air
with water, like wet sponge, is less remarkable
than the continuance for squeezing The sponge so to
speak and causing the diffused moisture To fall in
gentle rains, SHOWS, and dcws. The drying Of the
atmosphere, after it is saturated with water, is
phenomenon, without which it would never rain ;
nor could there be any springs, rivers land plants
or animals on the globe. This precipitation of
ter is effected by change of temperature, which
change is the result of the revolution of the earth
on its axis, and of solar heat. Day and Night
Spring, Summer, Autumn, and Winter, with their
ver-varying temperature, varying winds, and
clouds, and constantly changing humidity, arc all
results of fixed laws, which invite the research Of
every reasoning mind.
SOLAR HEAT.-Accordng to Professor Forbes,
the rays of heat coming from the sum- and passing
through the atmosphere in the shortest line, at the
latitude of Paris lose % per cent of their calorifc
power by the time they reach the earth. Rays that
strike the atmosphere at angle of only 25o part
with half their intensity, or heat, by the time they
touch the ground. The molecules OF air absorb
and radate heat into space, the same other pom
derablo bodies. Hence, no matter how clear the
atmosphere, neither the rising nor the setting sun
iinparts much light heat those parts OF the
so IL 3 Al
the meridian. The effect of solar rays the earth is
still further diminished morning and evening, by
the fact that fewer fall on any given area because
they mpnge upon its surface obliquely One can
look at the setting with impunity, not because
it emits ess heat light at that time but because
the rays are mostly absorbed and radated in pass
ing through many miles Of atmosphere before they
reach the eye oil the observer.
The facility with which solar heat pcnetrates and
the soil, TO the depth Of g. IL, Is, and "a
inches and the radiation OF heat from the earth the
leaves of plants and all other substances deserve
particular notice
distinction must be made between the radia-
ton of heat from the surface of any body, and the
transmission OF II through any substance, as iron,
wood, water mold soil. All these hold different
relations TO this peculiar element 1t is not intend
ed to take more than popular view Of this subject
At the time of seeding in spring, a single day is
sufficient 10 10 the depth OF inches, mel
low soil, recently ploughed. Two days Of sun will
warm the ground inches; and six days IL inches.
The fall Of warm rain a we'll drained, mellow
soil, greatly hastens the heating of the earth. On
the contrary, the fall of cold rain, much cold
water in the ground, greatly retards the rise of
temperature in TILED land. Heat and water
should be studied together, II one would obtain
clear idea of their joint Influence vegetation.
When water evaporates, il expands to l,696 times
Its former volume, and renders latent, or inscns-
bic, considerable amount Of active heat. Hence,
a wet piece of ground, from the surface of which a
good deal Of water cvaporatcs, is always cooled by
the loss Of sensible heat which rises in
por and departs far into the atmosphere.
The afr tla ~ -
capacity 10 hold water in the condition of diiused
invisible vapor. The lower strata Of air heated
much more by calo-ic radatcd from the earth than
by the absorption of heat from the in its pas
sage to the planet. Air thus heated becomes ex-
banded or rarihed, and specifically lighter than the
colder air above il. This causes the air within and
the tropics TO rise high above the surface OF the
earth, and flow over both north and south, toward
either pole; while colder and heavier air rushes la
toward the equator TO fill the empty space. These
erial currents detected in their courses by the
diurnal revolution of the earth, and by mountain
ranges whose submits often covered with eter
nal snow; and they still further modified by the
varying temperature of the ocean and its peculiar
streams.
Heat and water arc the fruitful parents Of winds
and clouds. When aqueous vapor il precipitated
in rain snow, heat that latent becomes again
sensible, and by increasing the capacity of the air
to hold water in the form Of vapor, prevents die
sstrous deluge Of this abundant element in nature
The laws which restrain the precipitation Of water
from the clouds less curious than those
winch cause IL 10 rain at all. lhe atmosphere must
approach saturatIon before il rain; and il
ally happens that the quantities which will fall on
given area one hundred feet above the ground, and
On the earth, arc unequal Large drops, in falling
through many feet OF dry air, become smaller by
constant evaporation, and may be wholly dssi
psted before they reach the earth. On the other
hand, quite small drops formed in cold regions,
high in the air, constantly condense more vapor in
falling through saturated atmosphere, and will
he many times larger when they reach .hc ground
than at their starting point.
10 illustrate the production Of rain, let us sup
pose that current Of air at 70o temperature, sat
urated with moisture, meets and mingics with
another current, also saturated, but having hcal
Of 500 Now, If the atmosphere at the mean TEN
pcraturc Of GO had capacity TO hold water as an
invisible vapor, equal 10 the mean Of 7O' and 50
is Obvious that no precipitation would take place
But such IL not the fact. The quantity Of water
held ia air heated from 60o 10 70o cannot be con
tanned in that heated from 500 To COZ. In othei
words, whatever cools air saturated with moisture
causes n cloud dew, mist, or rain.
Early and late frosts are produced by the radia