Green-Mountain freeman. [volume] (Montpelier, Vt.) 1844-1884, 1855-07-05
DIP. THOMPSON, EDITOR & PROPRIETOR.

ing depths in mines of different metals, and in
different varieties of rock.
I'd. The fact that copper mines become cooler,
though the depth increases, in proportion as the
ore diminshes.
4th. II is there said that the increase of tenn
perature can easily be accounted for by the
pressure of the atmosphere, and defective cirou-
lation
There are other and perhaps severer objections
to the theory in question, as indeed there are to
all theories of geognosy which have ever met
with Yet this theory seems to me to account
for all the phenomena revealed to us by the
study of geology, more satisfactorily than any
other; and many Of the objections seem to be
rather apparent than real do not propose to
enter upon any extended illustration or defense
Of the fre-theory, but simply to consider the
bearing upon it of the facts enumerated above.
And first, the temperature of the ocean wa
terss Tfesc, II lis said, shoald, ,a:in@aeeofdanes
with the theory, grow warmer as we descend,
and would be in state of ebullition where the
ocean is deepest, on account of their proximity
to the central fires. Now do not see that this
necessarily follows. The geological changes
which followed out the present bed of tho ocean,
were comparatively recent, as is abundantly ey-
denccd by marine shells on mountains now far
inland, by fresh water deposits of alluvium at
the bottom of the ocean, and by other proofs,
which it is needless now to cite I; and there can
be no very good ground for believing the solid
crust to be thinner under deep water, than in
elevated plateaus, like that of Eastern Asia. 1t
is evident that the oceanic waters cannot be af-
fected at great depths by solar heat, for two
reasons-the extremely small conducting power
of water, and the fact that the heated PARTICLES
become lighter, and remain upon the surface.
| Whatever heat, then, does affect the great mass
of waters, must come from beneath but this
not only is, but must be, slight, for it must de-
pend on two conditions, the distance of the GEN.
trail fires, and the power which the submarine
strata possess of transmitting heat. | can see
no good reason to consider the first to be less or
the latter greater, than upon the continents;
and here we know the sun to be the great foun
! tain of heat, irdeed almost the sole source.
From experiments, M. Peltier concludes the
amount of heat received annually from the SUM-
to be sufficient to melt layer of ice 46 feet
deep, enveloping the whole globe; while jim the
same way, the heat that reaches the earth's sur
face annually from the centre, has been estima-
ted capable of liquefying shell Of ice but one
fourth of an inch in thickness. This may be
considerable be nearly the amount of caloric
which the ocean receives from subterranean fires,
on account of the low conducting power Of the
subacent strata.
Observation shows us that the temperature Of
the ocean decreases continually, though irregu.
larly, as we descend, until we reach GER
tain depth and varing with the latitude, be.
yond which poilit - 2 niation. An
tat the DEPTH a y. Ne .surfac!
was at S3o and Til temperatufe i
probably higher than the true one, on account
of the compression of the bulb of the thermom-
eter at SO great depth Experiment has proved
conclusively that the oceanic waters, beyond
the invariable point mentioned above, maintain
a uniform temperature of about 1889 Fah.,
which is that of the maximum density of water
This point is f200 fathoms below the surface a
the equator, whence It rises gradually towards
the poles, coming to the surface at $40 north
latitude, and again sinking, till at about 70'
north latitude, it is $50 fathoms below the sur
face :; and the superficial water is now colder
than that at great depths Mr.. Scoresby found
in the Polar Ocean an increase of Go at th'
depth of l2O fathoms; Mr.. Fisher, of 9.50 a
1873 fathoms and Lieut.. Beechy, of 100 at 70(
fathoms. These observations, and others Of ;
similar character, which might cite, 50 as fal
towards proving the doctrine of internal heat
as those made in equatorial seas, with diiferen
result, towards confuting it. But, in truth
these facts affect the theory neither in the on
way, nor the other. The inconstant rate of in
crease, which one can not fail to remark in tn
observations just cited, and the equally varying
: rate Of decrease in tropical seas, would lead u
. to suspect the great influence of marine current
: upon oceanic temperature and these togethe
with the invariable law, that water expands an,
rises at all temperatures both above and below
y $3.50, are sufficient to account for all phenom
+ ena of this kind. The view taken here is con
: firmed by the fact that the waters Of the Med
10 terranean, which is in great measure shut o
from the influx of polar currents, maintain
y greater degree of heat than is found at CORES
N ponding depths in the Atlantic. The varyin
temperature, then, of deep seas, as well as {
u fresh water lakes, is precisely what we migt
'e expect to find, from previous acquaintant
with the properties of water.
al I'd and Sd. Copper mines are hotter tina
y lead mines, and become cooler as the ore dimil
sc shes, though the depth increases" A sing
~ fact of this kind does not seem to me to weig
much, when it is opposed by countless observ
'' tons of an exactly opposite character. The
u must be u local cause lfor such local phenon
70 enon and it is possible we need not 60 far
60 find it, am Inclined to ascribe it to the diffe
- ent power of conducting heat, possessed by tt
'' different rocks and metals. Veins of the latt
may be, and probably are, connected in son
way with some source of heat, whether with
region Of intense chemical action, or with fir
= at the earth's CENTER and the heat of the rot
or mine must depend in great part upon the sp