"And it does not roast us!" exclaimed Michel.
"No," replied Barbicane, "because the terrestrial atmosphere absorbs four-tenths of the solar heat; besides, the quantity of heat intercepted by the earth is but a billionth part of the entire radiation."
"I see that all is for the best," said Michel, "and that this atmosphere is a useful invention; for it not only allows us to breathe, but it prevents us from roasting."
"Yes!" said Nicholl, "unfortunately, it will not be the same in the moon."
"Bah!" said Michel, always hopeful. "If there are inhabitants, they must breathe. If there are no longer any, they must have left enough oxygen for three people, if only at the bottom of ravines, where its own weight will cause it to accumulate, and we will not climb the mountains; that is all." And Michel, rising, went to look at the lunar disc, which shone with intolerable brilliancy.
"By Jove!" said he, "it must be hot up there!"
"Without considering," replied Nicholl, "that the day lasts 360 hours!"
"And to compensate that," said Barbicane, "the nights have the same length; and as heat is restored by radiation, their temperature can only be that of the planetary space."
"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
"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!"
"Yes," replied Michel, with an amiable swagger, "I have a few ideas of that sort."
"But that idea does not spring from Michel," answered Nicholl.
"Well, then, I am a plagiarist."
"No doubt about it. According to the ancients, the Arcadians pretend that their ancestors inhabited the earth before the moon became her satellite. Starting from this fact, some scientific men have seen in the moon a comet whose orbit will one day bring it so near to the earth that it will be held there by its attraction."
"Is there any truth in this hypothesis?" asked Michel.
"None whatever," said Barbicane, "and the proof is, that the moon has preserved no trace of the gaseous envelope which always accompanies comets."
"But," continued Nicholl, "Before becoming the earth's satellite, could not the moon, when in her perihelion, pass so near the sun as by evaporation to get rid of all those gaseous substances?"
"It is possible, friend Nicholl, but not probable."
"Because-- Faith I do not know."
"Ah!" exclaimed Michel, "what hundred of volumes we might make of all that we do not know!"