The enormous size of the lunar volcanoes is not so difficult to
account for when we remember how slight is the force of lunar gravity
as compared with that of the earth. With equal size and density,
bodies on the moon weigh only one-sixth as much as on the earth.
Impelled by the same force, a projectile that would go ten miles on
the earth would go sixty miles on the moon. A lunar giant thirty-five
feet tall would weigh no more than an ordinary son of Adam weighs on
his greater planet. To shoot a body from the earth so that it would
not drop back again, we should have to start it with a velocity of
seven miles per second; a mile and a half per second would serve on
the moon. It is by no means difficult to believe, then, that a lunar
volcano might form a crater ring eight or ten times broader than the
greatest to be found on the earth, especially when we reflect that in
addition to the relatively slight force of gravity, the materials of
the lunar crust are probably lighter than those of our terrestrial
rocks.
For similar reasons it seems not impossible that the theory mentioned
in a former chapter -- that some of the meteorites that have fallen
upon the earth originated from the lunar volcanoes -- is well founded.
This would apply especially to the stony meteorites, for it is hardly
to be supposed that the moon, at least in its superficial parts,
contains much iron.
Pages:
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197