New-York tribune., 1903-02-14
POWER FROM THE EARTH'S HEAT.

In "Cassier's Magazine for February Pro-
fessor William Hallock, of Columbia Unlversily'
briefly but succinctly discusses the idea or u'li-
izng the internal heat of the earth for lncus-
trial n,rnoses At g. level 100 feet below the
surface The Temperature remains uniform the
year round From that point downward 1t In
creases about one degree for every sixty feee.
At first the rate may not be quite so great but
below 5000 and 1000 feet it is somewhat
greater. This is the gradient at Wneenhs'
where a. well has been sunk 4,5O0 feet, and at
West Eliza BETH near Pittsburg, where depth
of $3.50 feet has been attained. By going down
two or three miles at these places much more
rapid increase might be expected Still. there
are a few especially favored sites where one
could work more advanta geously. In the Com
stock mine for instance, temperature of liu
degrees has been experienced, and If a hole 5,OOO
feet deep were sunk there. heat should be founo
greatly exceeding that of boiling water Again,
the fluid which comes up in some of the Yellow
stone Park geysers has a temperature OF 19o
degrees and speculation on the result OF trying
to tap that supply or OF locating heat motor
on the slopes of Pelee, is most inviting
The particular type of engine employed to
convert the heat thus sought would dictate the
depth to which it would be necessary to 60 In
any case the machinery could be kept the
shafts. one for the downward movement Of cold
water and the other one for the upward flow
of hot liquid, and if a capacious reservoir were
blasted out at the bottom to hold the water
while it was absorbing heat from the enclosing
rock the rest would be comparatively simple
1t would then be necessary to decide Whether
to use in the engine itself some substance like
carbonic acid, sulphur dioxide or ether, which
Will vaporize and expand at a lower tempera-
ture than water does, or to employ steam. In
the former case it would be necessary to go
down only far enough to obtain a temperature
of $50 or 200 degrees while in the latter 300 de-
grees more would be requisite. The first of
these two systems is practicable, beyond doubt
but it Is not economical as the other, since
there is apt to be little waste Of vapor in spite
-of the most perfect fitting of joints Ether
carbonc acid gas and sulphur dioxide would
cost something. while water would not. On the
whole, therefore, the greater depth would prob
ably be found the more satisfactory.
The Importance of this general proposition
like that of utilizing the tides, grows of the
fact that the worlds fuel supply is compare
lively ephemeral resource. while the two agencies
here referred to are likely to last long the
human race, If not longer. To all intents and
purposes they inexhaustible To-day it
might be too expensive to get power in either
of these two ways; tomorrow 1t may be neces-
sary. The matter therefore deserves careful con-
sderation 1t is greatly to be wished that the
means be provided for boring two three ex-
perimental holes to depth of three miles in
order to reveal the temperature gradient further
down than man has hitherto gone 1t would
then be important to learn. by practical test
and not mere computation. the maximum
amount OF. power that can be derived from
single pair of holes. Are there any limitations
which fix this, say at % or 100 horsepower?
How widely distributed must such plants be
not to interfere with one another? Would it not
be possible. electrically or otherwise. to concen-
trate the output of twenty or thirty motors of
the type here considered? These and other
questions would need solution after the main
one was disposed of. but they should not prove
difficult.