“A pretty country, that!” exclaimed Michel. “Never mind! I wish I was there! Ah! my dear comrades, it will be rather curious to have the earth for our moon, to see it rise on the horizon, to recognize the shape of its continents, and to say to oneself, ‘There is America, there is Europe;’ then to follow it when it is about to lose itself in the sun’s rays! By the bye, Barbicane, have the Selenites eclipses?”
“Yes, eclipses of the sun,” replied Barbicane, “when the centers of the three orbs are on a line, the earth being in the middle. But they are only partial, during which the earth, cast like a screen upon the solar disc, allows the greater portion to be seen.”
“And why,” asked Nicholl, “is there no total eclipse? Does not the cone of the shadow cast by the earth extend beyond the moon?”
“Yes, if we do not take into consideration the refraction produced by the terrestrial atmosphere. No, if we take that refraction into consideration. Thus let <lower case delta> be the horizontal parallel, and p the apparent semidiameter—”
“Oh!” said Michel. “Do speak plainly, you man of algebra!”
“Very well, replied Barbicane; “in popular language the mean distance from the moon to the earth being sixty terrestrial radii, the length of the cone of the shadow, on account of refraction, is reduced to less than forty-two radii. The result is that when there are eclipses, the moon finds itself beyond the cone of pure shadow, and that the sun sends her its rays, not only from its edges, but also from its center.”
“Then,” said Michel, in a merry tone, “why are there eclipses, when there ought not to be any?”
“Simply because the solar rays are weakened by this refraction, and the atmosphere through which they pass extinguished the greater part of them!”
“That reason satisfies me,” replied Michel. “Besides we shall see when we get there. Now, tell me, Barbicane, do you believe that the moon is an old comet?”
“There’s an idea!”