For light in the hollow sphere
(p. 576) provision might in some manner be contrived."
According to the most recent experiments of Reich, the result obtained is
5.44; that is to say, the mean density of the whole Earth is 5.44 times
greater than tht of pure water. As according to the nature of the
mineralogical strata constituting the dry continental part of the Earth's
surface, the mean density of this portion scarcely amounts to 2.7, and the
density of the dry and liquid surface conjointly to scarcely 1.6, it follows
that the elliptical unequally compressed layers of the interior must greatly
increase in density toward the center, either through pressure or owing to
the heterogeneous nature of the substances. Here again we see that the
vertical, as well as the horizontally vibrating pendulum, may justly be
termed a geognostical instrument.
The results obtained by the employment of an instrument of this kind have
led celebrated physicists, according to the difference of the hypothesis
from which they started, to adopt
p 171
entirely opposite views regarding the nature of the interior of the globe.
It has been computed at what depths liquid or even gaseous substances would,
from the pressure of their own superimposed strata, attain a density
exceeding that of platinum or even iridium; and in order that the
compression which has been detrmined within such narrow limits might be
brought into harmony with the assumption of simple and infinitely
compressible matter, Leslie has ingeniously conceived the nucleus of the
world to be a hollow sphere, filled with an assumed "imponderable matter,
having an enormous force of expansion.
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