Litchfield enquirer., 1840-05-07
THEORY OF DEW.

C.-Come on then.-IEreunt
THEORY OF DEW.
Notwithstanding the researches of DIR.
Wells, and others, upon the subject of dews,
there are many who still remain either in to-
tai ignorance of the principles of the depo-
sitlon Of the moisture called dew, Or hold to
the old theory that it is caused by the air
alone becoming COLDER The ancient Greeks
observed the fact, that dew was deposited in
clear nights, and not in windy or cloudy
ones, and every barefooted boy who goes out
carly in the morning, knows that it is much
more abundant on the grass by the wood
side, than it is upon the sand or gravel In the
road itself. DR.. Wells, of England, made
many experiments upon the subject; and
from the facts thus ascertained, explained
the cause OF the phenomena, in treatise
which he published some time ago. He as
certained the cause OF the deposit of moist
ure in the form of dew, to be the radiation
or throwing off the heat imbibed by the sun,
which thus cools the particles Of air that
come in contact with it, and causes the mois-
ture which was in the warm air to be con-
densed. 1t may be we'll, for the better un.
derstanding of the theory, to state, in the
first place, that as all bodies receive heat
more or less easily, 30 they part with it, or
rudiate it more or less easily. Some bodies
will part with, or radiate the heat which
they have received, as fast again as other
bodies. Hence they become cooled before
the others. Warm air will hold more mois-
ture than cold air: therefore, the body
which radiates heat fastest, becomes cool
first. Grass parts with its caloric, or heat,
much faster than sand or gravel-hence 1t
has more dew upon it.
The following experiments may not DO
uninteresting to some Of our readers. After
long period Of drought, when the air was
very still, and the sky serene, DR.. Wells ex-
posed to the sky, twenty eight minutes be-
fore sunset, previously weighed, parcels OF
wool and swandown, upon smooth unpaint-
ed and perfectly dry fir table, five feet long,
three broad, and three feet in height, which
had been placed an hour before. In the sun
shine, in a large, level grass field.
The wool, twelve minutes after shutdown,
was found to be fourteen degrees colder than
the air, and to have acquired no weight
much smaller than that of the wool, was at
the same time thirteen degrees colder than
the surrounding air. At the same time, the
grass was fifteen degrees colder that the air
four feet above the ground. From such ex-
periments, he established the proposition,
that bodies must become colder than the
surrounding air, before they become dewed.
He also explained the reason why there
was no dew in cloudy nights. II is because
the clouds act as reflectors, and throw the
heat back again; in the same manner as the
bright tin top Of O tin baker throws down or
reflects the heat down upon the bread. A
blanket, or umbrella, put over any body,
would prevent the dew settling on that body
for some time. although it was falling all
around it. 49,
On this principle, vines, and other things,
are protected from frosts, by putting blan-
ket or covering over them, at night.
Frost is dow, frozen. BY putting the COW
ering over the body,i 1t reflects heat back,
and prevents, for some time, the dew being
deposited upon what it covers.--M0tne paper.
M,,sic.--The following excellent remarks
on the subject of Music, and on the impor-
lance of teaching the harmonious art in our
public schools, are from the pen OF Rev. John
Todd, of Philadelphia:
"God has made the ear to love Music but
this is not all. He has created a most won.
derful Musical instrument for the use of eve-
nv one. Between the top of the throat and the
root of the tongue, he has made an enlarge
ment: A cavity of two or three inches, and
most curiously lined it with delicate men,
branes, so stretched that the air passing thro
them makes sound ns through a clarionet.
This would be curious instrument even If 1t
admitted of no variations of sound but it is
furnished with fine cartileges which contract
and expand the cavity at pleasure, in differ
ent ways, so as to give different vibrations,
and of course different tones. In this small
space, then, in the throat of every human be-
ing, is an instrument with n compass of from
two to three octaves, which has the COM
mand Of every scmi-tone and subdivision of
note, swell, trill, &c, and not necessarily
exposed TO the imperfections of.artificial in-
struments, but so clear, so rich, so sweet, as
to be the highest standard Of comparison, in
these points, for the flute, clarionet, piano
and organ. Now think of this wonderful in
strument, bestowed upon every one by the
hand of God, think how the ear is so created
TO delight in melody, that the brightest and
sweetest emblem Of heaven is the innumera-
bic company Of saints and angels around the
throne singing and praising God and the
lamb: and then tell me if singing ought no
to have a very prominent place in teaching
children-in forming their characters
| plead on this subject with the earnestness OF
one who was himself neglected in this PartIc'
ular in childhood, and who has, in conse
auencc, suffered loss which no language
can describe. The wrong is no less severe
because the child docs not feel tho loss at th'
time. Iplead for every child"