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On the southern side of the central rano;e
of the Grecian and Pennine Alps, there are
also numerous warm springs. The best
known are those of St. Didier, near Cormayeur,
almost immediately under the southern
escarpement of Mont Blanc. The warmest
spring at Cormayeur has the temperature of
94° Farenheit. I have before mentioned
that I was prevented by the weather from
visiting these baths, when I had arrived at
the foot of the little St. Bernard. I am
informed that several of the retired valleys
in Piedmont, at the foot of the central
range, are subject to earthquakes, during
which the earth has opened, or sunk down
in various parts, though these effects have
been too local, to excite attention at a distance.
With these facts before us, it seems most
unreasonable to doubt, that the hot springs
in the Alps owe their temperature to subterranean
fire, as much as those near
Naples, or in Auvergne, or the Geysers in
Iceland, though the earth may no where
have thrown out lava in their vicinity.
That subterranean heat produces sensible
effects at a distance from the thermal
waters, may, I think,' be fairly inferred
from the observation of Saussure, on the
thawing of the bottom of the glaciers
durino; seasons of intense frost. This
cannot be owing to the effects of the
mean temperature of the earth, as some
have supposed, for were it so, we should
observe the earth thawing the ice in other
situations, and as the ground under the
glaciers has, from 'unknown ages, been
shielded from the solar rays, it must consequently
derive less heat from that source,
than any other parts of the earth’s surface.
The constant occurrence of thermal
springs in deep valleys, near where the
rocks called primary are covered by the
secondary strata, will, 1 think, admit of a
satisfactory explanation. The granitic
rocks and those of mica-slate are intersected
by so many fissures, that the thermal
waters could not rise through them to any
great height above the valleys, where these
rocks are uncovered ; and even were they to
rise above them, they would be so intermixed
with surface-waters, that their temperature
would be reduced to that of rain
water. But where the primary rocks are
protected more or less from the surface-
waters, by a great thickness of secondary