e noticed that their banks were exceedingly steep. They were long
parallel ramparts; with a little imagination they might be taken for
long lines of fortifications raised by Selenite engineers.

Some of these furrows were as straight as if they had been cut by line,
others were slightly curved through with edges still parallel. Some
crossed each other. Some crossed craters. Some furrowed the circular
cavities, such as Posidonius or Petavius. Some crossed the seas, notably
the Sea of Serenity.

These accidents of Nature had naturally exercised the imagination of
terrestrial astronomers. The earliest observations did not discover
these furrows. Neither Hevelius, Cassini, La Hire, nor Herschel seems to
have known them. It was Schroeter who in 1789 first attracted the
attention of _savants_ to them. Others followed who studied them, such
as Pastorff, Gruithuysen, Boeer, and Moedler. At present there are
seventy-six; but though they have been counted, their nature has not yet
been determined. They are not fortifications certainly, anymore than
they are beds of dried-up rivers, for water so light on the surface of
the moon could not have dug such ditches, and there furrows often cross
craters at a great elevation.

It must, however, be acknowledged that Michel Ardan had an idea, and
that, without knowing it, he shared it with Julius Schmidt.

"Why," said he, "may not these inexplicable appearances be simply
phenomena of vegetation?"

"In what way do you mean?" asked Barbicane.

"Now do not be angry, worthy president," answered Michel, "but may not
these black lines be regular rows of trees?"

"Do you want to find some vegetation?" said Barbicane.

"I want to explain what you scientific men do not explain! My hypothesis
will at least explain why these furrows disappear, or seem to disappear,
at regular epochs."

"Why should they?"

"Because trees might become invisible when they lose their leaves, and
visible when they grow again."

"Your explanation is ingenious, old fellow," answered Barbicane, "but it
cannot be admitted."

"Why?"

"Because it cannot be said to be any season on the surface of the moon,
and, consequently, the phenomena of vegetation on the surface of the
moon cannot be produced."

In fact, the slight obliquity of the lunar axis keeps the sun there at
an almost equal altitude under every latitude. Above the equatorial
regions the radiant orb almost invariably occupies the zenith, and
hardly