yioa innossiw 
522 THE SCIENTIFIC MONTHLY. 
the latitude of New York would give heat enough to boil water at a depth of 8,100 
feet, and 3,000° F., the fusing point of iron, at a depth of 28 miles.”— Dana. 1 
The phenomena of the flow of naturally heated water from the earth has been 
the subject of speculation from a very early date, and attempts have been made to J 
explain it upon the principal of chemical changes taking place beneath the surface j 
of the earth, and many ingenious theories have been advanced in its support. It J 1 
is assumed that chemical changes take place beneath the surface in local situations, j 
and that these local chemical changes are sufficient to account for the many vol- J 
canic actions manifested; and, moreover, that to these chemical changes are ' 
attributed all the phenomena of central heat, hot springs, mud volcanoes, etc. 
The chemical theory might, indeed, afford a satisfactory explanation of cer- 1 
tain phenomena, but the theory most generally entertained and the one, seemingly, | 
most entitled to credit, is that which regards the water as having been rendered j 
warm or hot by contact with the heated strata or lava over which, in its subterra- j 
nean passage, it courses. That they are of volcanic origin would seem to follow j 
from the fact that they are found in regions of later geological formation, and 
where the country is of comparative recent volcanic origin. 
“ The theory of mountain building, advocated by Mrssrs. Hunt, Mallet and 
Le Conte, call mountain corrugations a result of mechanical work, due to hori¬ 
zontal pressure (a function of the secular cooling of the earth), and announces as | 
a second result of the same work the development of heat in the loci of the work, j *- 
It is held that in some places corrugation does not take place, but instead, there j 
n results a local crushing of the rock, accompanied by sufficient heat to produce | 
§ local fusion and furnish material for volcanoes. If this be the true theory of vol-i 
< canoes, then the equilibrium of the heat of the 'crust may be disturbed by the 1 
: production of local maxima, not only where the rocks are pierced by molten dikes,; 
% but also in the places, not necessarily very deep-seated, where lava is found, and: 
ill also along the axis of corrugation, and these regions would naturally contain hot( 
8 springs. * * * The most intense action would be prodnced by recent dikes, j 
& Where the discharge is small, and the temperature high, the source of heat cannot j 
g be remote, else the heat would have been lost in transit; and, as this is the rule | 
owith geysers, they are probably regarded with propriety as strictly volcanic phe- 
nomena, indicating the recent injection near the surface of hot lava, whether or 1 
not it has been extruded.”— Gilbert. 
And as to the origin of volcanoes, the best received theory is that the center 
f of the earth is in a fiery—a molten state—and that volcanoes are but the openings, 
chimneys or flues to this central sea of heated molten matter, and that from this j 
source spring all the various phenomena of the increase of heat' as we descend 
beneath the outer crust of the earth—of earthquakes, volcanoes, etc., etc. 
A fact that gives strong support to the volcanic origin of thermal springs is j 
that they are found in every instance in what are known as “ corrugation ” strata j 
Botanical 
cm copyright reserved garden 
