beneath, it fails wholly to explain many of the most
important circumstances observable as to the distribution and movements
of existing Volcanoes on our globe.

It affords no adequate explanation of the configuration of the lines of
Volcanoes, nor of their occurrence in the ocean bed, nor of their
existence in high latitudes, near the Poles, where, no matter how or at
what rate our globe cooled from liquidity, the crust must be thickest;
nor of the independence of eruptive action of closely adjacent volcanic
vents; nor of the non-periodicity, the sudden awakening-up to activity,
the as sudden exhaustion, the long repose, the gradual decay of action
at particular vents, and of much more that might be stated and
sustained as difficulties left by that theory unexplained, or that are
of a nature even opposed to it.

The researches of the last few years have, however, as it appears to me,
rendered any theory that demands as its postulates a _very thin crust_,
and a universal liquid nucleus beneath it, absolutely untenable.

Without attaching any importance to the arguments of Mr. Hopkins, based
upon precession and nutation, it appears to me, on various other
grounds, some of which have been urged by Sir William Thompson, that the
earth's solid crust is not a thin one, at least not thin enough to
render it conceivable that water can ever gain admission to a fluid
nucleus, if any such still exist, situated at so great a depth; and
without such access we can have no Volcano. It is not necessary to go to
the extent of a crust of 800 or 1,000 miles thick: with one of half the
minor thickness, I believe it may be proved, on various grounds,
hydraulic amongst others, that neither water could reach the nucleus,
nor the liquid matter of the nucleus reach the surface. Mr. Hopkins
having proved to his own satisfaction an enormous thickness for the
crust, and seeing clearly the difficulties that this involved to the
generally accepted volcanic theory, and having no other to substitute
for it, fell back upon that most vague and weak notion of the existence
of isolated lakes of liquid rock, existing at comparatively small depths
beneath the earth's surface within the solid and relatively cold crust,
each supplying its own Volcano, or more than one, with ready-made lava.
What is to produce these lakes of fused matter in the midst of similar
solidified matter? what is perpetually to maintain their fluidity in the
midst of solid matter c