It is at least fifty or
sixty miles long and runs along the base of the _Apennines_ in a line
almost perfectly straight. Does not its parallelism with the mountain
chain suggest a causative relation? See that other mighty _rill_, at
least a hundred and fifty miles long, starting directly north of it and
pursuing so true a course that it cleaves _Archimedes_ almost cleanly
into two. The nearer it lies to the mountain, as you perceive, the
greater its width; as it recedes in either direction it grows narrower.
Does not everything point out to one great cause of their origin? They
are simple crevasses, like those so often noticed on Alpine glaciers,
only that these tremendous cracks in the surface are produced by the
shrinkage of the crust consequent on cooling. Can we point out some
analogies to this on the Earth? Certainly. The defile of the Jordan,
terminating in the awful depression of the Dead Sea, no doubt occurs to
you on the moment. But the _Yosemite Valley_, as I saw it ten years ago,
is an apter comparison. There I stood on the brink of a tremendous chasm
with perpendicular walls, a mile in width, a mile in depth and eight
miles in length. Judge if I was astounded! But how should we feel it,
when travelling on the lunar surface, we should suddenly find ourselves
on the brink of a yawning chasm two miles wide, fifty miles long, and so
fathomless in sheer vertical depth as to leave its black profundities
absolutely invisible in spite of the dazzling sunlight!"
"I feel my flesh already crawling even in the anticipation!" cried
Ardan.
Pages:
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234