The travelers discussed the origin of these strange rays; but they could not determine their nature any more than terrestrial observers.
“But why,” said Nicholl, “should not these rays be simply spurs of mountains which reflect more vividly the light of the sun?”
“No,” replied Barbicane; “if it was so, under certain conditions of the moon, these ridges would cast shadows, and they do not cast any.”
And indeed, these rays only appeared when the orb of day was in opposition to the moon, and disappeared as soon as its rays became oblique.
“But how have they endeavored to explain these lines of light?” asked Michel; “for I cannot believe that savants would ever be stranded for want of an explanation.”
“Yes,” replied Barbicane; “Herschel has put forward an opinion, but he did not venture to affirm it.”
“Never mind. What was the opinion?”
“He thought that these rays might be streams of cooled lava which shone when the sun beat straight upon them. It may be so; but nothing can be less certain. Besides, if we pass nearer to Tycho, we shall be in a better position to find out the cause of this radiation.”
“Do you know, my friends, what that plain, seen from the height we are at, resembles?” said Michel.
“No,” replied Nicholl.