d into heat
than I have attributed to them by ranging them as only equal to the
granites, etc.--then we obtain a mean co-efficient for the entire
thickness of crust of 100 miles of 6,472 British units of heat,
developable from each cubic foot of its material, if crushed to powder.
It results from this that each cubic mile of the mean material of such
a crust, when crushed to powder, developes sufficient heat to melt 0.876
cubic miles of ice into water at 32 deg., or to raise 7.600 cubic miles of
water from 32 deg. to 212 deg. Fahr., or to boil off 1.124 cubic miles of
water at 32 deg. into steam of one atmosphere, or, taking the average
melting point of rocky mixtures at 2,000 deg. Fahr., to melt nearly three
and a-half cubic miles of such rock, if of the same specific heat.

Of the heat annually lost by our globe and dissipated into space,
represented by 777 cubic miles of ice melted, as before stated, the
chief part is derived from the actual hypogeal source of a hotter though
not necessarily fused nucleus, and nearly, if not wholly, is quite
independent of the heat of Vulcanicity, which is developed as a
consequence of its loss or dissipation. But were we to take the extreme
case, and suppose it possible that all the heat the globe loses annually
resulted from the transformation of the work of internal crushing of its
shell, we shall find that the total volume of rock needed to be crushed
in order to produce the required amount of lost heat is perfectly
insignificant as compared with the volume of the globe itself, or that
of its shell. For, as 1.270 cubic miles of crushed rock developes heat
equivalent to that required to melt one cubic mile of ice to water at
32 deg., and if we assume the volume of our globe's _solid_ crust to equal
one-fourth of the total volume of the entire globe, 987 cubic miles of
rock crushed annually would supply the whole of the heat dissipated in
that time. But that is less than the _one sixty-five millionth_ of the
volume of the crust only.

But a very small portion of the total heat annually lost by our globe
is sufficient to account for the whole of the volcanic energy of every
sort, including thermal waters, manifested annually upon our earth. In
the absence of complete data, we can only approximately calculate what
is the annual amount of present volcanic energy of our planet. This
energy shows itself to us in three ways: 1. The heating or fusing of the
ejected solid matters at volca