us. Some had a width of thirty kilometres over a
length that could not be estimated.

The travellers discussed the origin of these strange rays, but they
could not determine their nature any better than terrestrial observers.

"Why," said Nicholl, "may not these rays be simply the spurs of the
mountains reflecting the light of the sun more vividly?"

"No," answered Barbicane, "if it were so in certain conditions of the
moon they would throw shadows, which they do not."

In fact, these rays only appear when the sun is in opposition with the
moon, and they disappear as soon as its rays become oblique.

"But what explanation of these trails of light have been imagined?"
asked Michel, "for I cannot believe that _savants_ would ever stop short
for want of explanation."

"Yes," answered Barbicane, "Herschel has uttered an opinion, but he does
not affirm it."

"Never mind; what is his opinion?"

"He thought that these rays must be streams of cold lava which shone
when the sun struck them normally."

"That may be true, but nothing is less certain. However, if we pass
nearer to Tycho we shall be in a better position to find out the cause
of this radiation."

"What do you think that plain is like, seen from the height we are at?"
asked Michel.

"I don't know," answered Nicholl.

"Well, with all these pieces of lava, sharpened like spindles, it looks
like 'an immense game of spilikins,' thrown down pell-mell. We only want
a hook to draw them up."

"Be serious for once in your life," said Barbicane.

"I will be serious," replied Michel tranquilly, "and instead of
spilikins let us say they are bones. This plain would then be only an
immense cemetery upon which would repose the immortal remains of a
thousand distinct generations. Do you like that comparison better?"

"One is as good as the other," answered Barbicane.

"The devil! You are difficult to please," replied Michel.

"My worthy friend," resumed the prosaic Barbicane, "it does not matter
what it looks like when we don't know what it is."

"A good answer," exclaimed Michel; "that will teach me to argue with
_savants_."

In the meantime the projectile went with almost uniform speed round the
lunar disc. It may be easily imagined that the travellers did not dream
of taking a minute's rest. A fresh landscape lay before their eyes every
instant. About half-past one in the morning they caught a glimpse of the
summit of another mountain. Barbicane consulted h