packing, hence that which will yield most to the pressure,
hence that which is likely to take place, is when they are all
regularly arranged facing the same way. Such an arrangement we
call crystalline. Just so when they want to pack the most
people into the car of an elevator they ask them to all face to
the front. Keep this metaphor a moment. Any one who should try
to penetrate such a crowd would find it a hard job. They would
offer a very effective rigidity. Now suppose them to sweat in
those confined quarters their fat away, their phlogiston, their
caloric. If the walls of the car remained rigid while the
individuals therein shrunk they might after a while be able to
turn around or even move around in a car. Such is then the
supposed condition of the atoms in the FOURTH, the central,
layer of the earth's crust. This assumes that the middle layer
is rigid and sustains itself, like the shell of a nut, as in
the figure, while within the atoms are in a less rigid
condition. That such a shell might be self-sustaining is
suggested by an experiment of Bridgman, who put a marble with a
gas bubble in it under a pressure of something like 150,000
pounds to the square inch without producing any perceptible
change.

As loss of energy from the earth's interior went on this
central core of gas would enlarge until the middle shell was
hardly self-supporting. Then, probably at some time of
astronomic strain when the earth's, orbit was extra elliptical,
it would collapse, in collapsing generate heat, and so stop the
process. The collapse would be transmitted to the viscous layer
which might be increased, motions set up in it, and so a
wrinkling of the outer thin crust on which we live.