The Southern herald., 1885-12-19

A- H4I7H-AAs@
iFrust b foras dsW, Il Is ssps
sa,ths ssh's sgE5ass upon hafhszs
isHees. beldisgs &c. d preasslE d
H& maeaar = the shsrklinf asH Nd
e she gzszs g ths mozturs wtich sst
sFahss everything apaA the s1rizs5 Q
the earth during ths cool hours Of til
night Frost IS deposited only uBds
suoh circumstances as would cause
deposit Of dew were. he tsnPersturU
AigheE. Bat there are tines in which
trost Is seen upon the ground or on the
grass and low hsrbsge when It is not q
b perceived upoB anything that is oves
a foot above the surface This Is due q
The fact that an active sFspOrstioa is 90
ing on ron the surface Of the earth, al
the samstime that the tsmperature is
near the freezing point but stiIl above
II and the refrigsrstisg effect Of the
evaporation Is sufficient to lower the
temperature Of the soil q few degrees
and so produce the freezing which
would not otherwise occur.
Frost. as regards its effect upon
growing tender vegetation. is simply
Pressing. or really the reduction Of
temperature below the freezing point
at which water is changed into
Ice Ths change is accompanied by
an increase in the bulk or an
expansion of the water to the extent of
one-ninth. which is sufficient TO burst
the cells Of such tender and succulent
vegetable tissue as Is unable to resist
the pressure or to expand under it, but
1t is not always that these cells are
ruptured in this way by frost A DO
tato nber. for instance. when slightly
Frozen, is much changed in its charac-
ter and yet the cells are not ruptured
in all cases. The cold has a chemical
effect and changes the starch of the
cells into sugar to such an extent as tc
give a sweet tasts to the potato, even
when the water in the potato has no,
been frozen solid and the cells have NOT
been broken up. A similar result han.
pens to other tender vegetation, some |
of which is injured or killed BY low
temperature, which. however, is still
above the freezing point The effect Of
frost upon corn, for instance. when
ne cold is not sufficient to freeze the
ohage Is evidently q chemical effect,
ust as the plunging Of a leaf into hot
Vater would scar and burn it. Tobacco
! affected in precisely the same way;
ne leaves being blackened by cold as
'ell as BY a heat Of one hundred and
wenty degrees. when 1t is continued
or sufficient time. In short there is
0 doubt that The damage done by frost
, tender vegetation is the result of q
Nv temperature more than to the actual
lpturing Of the cellular tissue and the
death of it.
The behavior of frost is remarkable
rost often occurs when the tempera.
ire OF the air Is above freezing point.
I'd there are times when the tempera-
ne falls below freezing and yet there !
no trost A remarkable instance oc.
Irred to US recently. A fog covered a
valley up to the height Of about thirty
ct and the elevated ground on each
10 was clear of it. The frost cut
me tobacco and potatoes on the hill
les but did not injure the corn on the A
v ground. This was clearly the re-
IL OF the protection of the fog, which
eVented radiation from the ground .
d also gave out warmth from itself az u
large quantity of latent heat in the q
'tery vapor was condensed into LIQUID .
on the growing corn, which was Il
thed in moisture that was warmer p
IN the air and gave out its warmth to c'
Above the fog there was nothing of q
$ going on, but quite the reverse; for tr
moist air there floating absorbed p'
heat from the soil as it was given be
Dy radiation and the evaporation is
ihe moisture took up this heat and at
dered 1t latent and non-efective. te
SO reduced the temperature that a Pi
Wy frost occurred there. 1t is in on
way that clouds operate to pre- or
ttrost when the Temperature it
low, and even reflect heat back fO
the surface which may have ris
'ped from it A dense smoke has brt
same effect and at such times in
'ly rises in the air. but floats a the
It distance above the surface and fici
IS out to the atmosphere the heat eff
ca 1t contains in the vapor mixed Pc
it. and which is condensed by the by
into visible moisture A bright, aci
: air, on the contrary, fayors evap- cor
ION from the ground and the air ma
tne surface, and the vapor thus lutt
Iuced tioats away in the upper air the
ying with it the one thousand units wit
'at in latent form into the upper is c
um, where 1t is condensed. and tun
large quantity Of heat is given out oug
.. The meaning Of one thousapd
OF heat may be realized when thew
ompared with one hundred and
y units. which are required to heat 4
old water up to the boiling point a clou
than five and one-half times AZ cost