The Hazlehurst signal. (Hazlehurst, Miss.) 1883-1885, 1885-11-26
FROST.
lts Nature. ana ERsets Upon Growing and
reudsv vaRstntton,

EIOub 10 ttOLuu uoWs ~ IN 's~f
on tho earth's surface. upon heritage.
fences, buildings. &C., In precisely tho
same manner rs tho sparkling dow up
on tho grass or tho moisture which sat
urates everything upon tho surface OF
tho earth during tho cool hours OF tho
night. Frost Is deposited only under
such circumstances us would cause
deposit Of dew were tho temperatutS
higher. But there are times In which
frost Is soon upon the ground or on tho
grass and low herbagc when 1t Is not to
bo perceived upon anything that Is over
a foot above tho surface. This is due to
tho fact that AN active evaporation Is 90.
ing on from the surface OF the earth. at
the same time that the temperature is
near the freezing point, but still above
II, and the rcfrigcrSting effect OF tho
svapora,ion Is sufficient to lower the
temperature of tho soil few degrees
and so produce tho freezing which
would not otherwise occur.
Frost. as regards It's effect upon
growing tender vegetation. Is simply
freezing. or really the reduction OF
temperature below tho freezing point
at which water Is changed into
leo. This change Is accompanied by
an increase in tho bulk or an
expansion Of the water to the extent Of
one. ninth. which Is sufficient to burst
the coils Of such tender and succulont
vegetable tissue as Is unable to resist
the pressure or to expand undor It, but
it 10 not always that these cells are
ruptured In this way by frost. A p6-
tato tuber. for instance. when slightly
frozen, Is much changed in Its charac-
ter. and yet the cells are not rupturcd
in oil cases. Tho cold has chemical
effect and changes the starch OF tho
cells into sugar to such an extent as to
give sweet taste to the potato. even
when the'water in tho potato has not
boon frozen solid and the cells have not
boon broken up. A similar result hap
pous to other teuder vegetation. some
Of which Is injured or killed by low
temperature, which, however, Is still
above the freezing point. The effect OF
u frost upon corn. for instance. when
tho cold Is not sufficient 70 freeze the
foliage Is evidently q chemical elect,
Just rs the plunging Of leaf into hot
water would scar and burn 1t. Tobacco
is affected in precisely the same way;
tho leaves being blackeped by cold as
we'll rs by heat Of one hundred and
twenty degrees, when Il is continued
Tor o sufficient time. In short. there is
no doubt that tho damage done by frost
to tender vegetation is the result OF a
low temperature moro than 70 the actual
ruptrring Of tho cellular tissue and the
consequent death Of It.
The behavior OF frost is remarkable.
Frost often occurs when the tempcra.
ture Of the air is above freezing point.
and there are times when the tempcra.
turc falls below freezing and yet thcre
Is no frost. A remarkable Instance &C.
currei to us recently. A fog covered q
q valley up to the height Of about thirty
feet and the elevated ground on each
side was clear Of It. The frost cut
some tobacco aud potatoes on the hill
sides. but did not injurc the corn on the
low ground. This was clearly the re-
suit Of the protection Of the fog. which
prevented radiation from tho ground
and also gave out warmth from itself, as
tho large quantity Of latent heat In the
watery vapor was condensed into liquid
upon the growing corn. which was
bathed in moisture that was warmer
than the air and gave out Its warmth to
It. Above tho fog there was nothing OF
this going on, but quite the reverse; for
the moist air there floating absorbed
the heat from the soil as 1t was given
out by radiation and tho evaporation
Of the moisture took up this heat and
rendered 4 latent and non.eilective,
and so reduced the temperature that n
heavy frost occurred there. 1t is in
this way that clouds operate to pre-.
vent frost when the temperature
10 low. and even reflect heat back
to the surface which may have
escaped from it A dense smoke has
the same effect, and at such times
rarely rises in the air. but floats q
short distance above the surface and
gives out to the atmosphere the heat
which It contains In the vapor mixed
with II, and which Is condensed BY the
cold into visible moisture. A bright,
clear air. on the contrary. favors evap.
grafton from the ground and tho air
near the surface, and the vapor thus
produced floats away In the upper ali
carrying with Il the one thousand units
Of heat in q latent form into tho upper
stratum, where II is condensed, and
this largo quantity OF heat Is given out
again. The meaning Of one thousand
units Of heat may be realized when they
! arc compared with one hundred and
eighty units, which arc required to heat
ice.cold water up to the boiling point
Moro than five and one-half. times as
much heat then arc required to vapor.
ize water or to produce evaporation as
are required to boil ice.co!d water.
That all this heat Is drawn from the soil
and tho air Immediately above 1t, and
Is carried up with vapor into the air.
and the vapor Is there condensed again
Into water. forming clouds or fogs
fully explains tho surprising phenom.
sna Of frost in low ground, while at
one hundred or two hundred feet above