aight. 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.

"I shan't regret it much if we never get to the Moon," growled
M'Nicholl; "I never hankered after it anyhow!"

By this time the Projectile had reached the fortieth degree of lunar
latitude, and could hardly be further than five hundred miles from the
surface, a distance reduced to about 5 miles by the travellers' glasses.
Away to their left appeared _Helicon_, a ring mountain about 1600 feet
high; and still further to the left the eye could catch a glimpse of the
cliffs enclosing a semi-elliptical portion of _Mare Imbrium_, called the
_Sinus Iridium_, or Bay of the Rainbows.

In order to allow astronomers to make complete observations on the lunar
surface, the terrestrial atmosphere should possess a transparency
seventy times greater than its present power of transmission. But in the
void through which the Projectile was now floating, no fluid whatever
interposed between the eye of the observer and the object observed.
Besides, the travellers now found themselves at a distance that had
never