p mines the
operatives work _in puris naturalibus_--and then upon an
oval-shaped cage made of papier mache, with a false bottom,
enclosed within which the miners were enabled to endure the
intense heat for a shift of two hours each day. The drilling was
all done by means of the diamond-pointed instrument, and the
blasting by nitro-glycerine from the outset; so that the
principal labor consisted in shoveling up the debris and keeping
the drill-point _in situ_.

Before proceeding further it may not be improper to enumerate a
few of the more important scientific facts which, up to the 1st
of November of the past year, had been satisfactorily
established. First in importance is the one alluded to above--the
rate of increase of temperature as we descend into the bowels of
the earth. This law, shown above to correspond exactly with the
law of attraction or gravitation, had been entirely overlooked by
all the scientists, living or dead. No one had for a moment
suspected that heat followed the universal law of physics as a
material body ought to do, simply because, from the time of De
Saussure, heat had been regarded only as a force or _vis viva_
and not as a ponderable quality.

But not only was heat found to be subject to the law of inverse
ratio of the square of the distance from the surface, but the
atmosphere itself followed the same invariable rule. Thus, while
we know that water boils at the level of the sea at two hundred
and twelve degrees Fahrenheit, it readily vaporizes at one
hundred and eighty-five degrees on the peak of Teneriffe, only
fifteen thousand feet above that level. This, we know, is owing
to the weight of the superincumbent atmosphere, there being a
heavier burden at the surface than at any height above it. The
rate of decrease above the surface is perfectly regular, being
one degree for every five hundred and ninety feet of ascent. But
the amazing fact was shown that the weight of the atmosphere
increased in a ratio proportioned to the square of the distance
downward.... The magnetic needle also evinced some curious
disturbance, the dip being invariably upward. Its action also was
exceedingly feeble, and the day before the operations ceased it
lost all polarity whatever, and the finest magnet would not
meander from the point of the compass it happened to be left at
for the time being.