Chapter XI

The Earth. The idea entertained by some celebrated men,
and others 197
Difficulties of forming a sphere out of a lens-shaped nebula 199
Various studies of the earth's interior made for special
purposes. Difficulty some people find in conceiving
how the average density of little over 5·66 can be
possible, the earth being a hollow sphere 200
What is gained by its being a hollow shell 201
Geological theories of the interior discussed. Volcanoes
and earthquakes in relation to the interior 202
Liquid matter on the interior surface of the shell, and
gases in the hollow, better means for eruptions than
magma layers 206
Focal depths of earthquakes within reach of water,
but not of lavas 207
Minute vesicles in granite filled with gases, oxygen and
hydrogen, but not water 209
The Moon. A small edition of the earth 211
Rotation stopped. Convulsions and cataclysms caused thereby.
Air, water, vapour driven off thereby to far-off
hemisphere. Liquid matter in hollow interior would
gravitate to the inside of the nearest hemisphere 212
Form and dimensions during rotation. Altered form after
it stopped 213
Agreeing very closely with Hansen's "curious theory" 214