"For two very good and sufficient reasons," answered Barbican. "In the first place, the terrestrial atmosphere absorbs the 4/10 of the solar heat. In the second, the quantity of solar heat intercepted by the Earth is only about the two billionth part of all that is radiated."
"How fortunate to have such a handy thing as an atmosphere around us," cried the Frenchman; "it not only enables us to breathe, but it actually keeps us from sizzling up like griskins."
"Yes," said the Captain, "but unfortunately we can't say so much for the Moon."
"Oh pshaw!" cried Ardan, always full of confidence. "It's all right there too! The Moon is either inhabited or she is not. If she is, the inhabitants must breathe. If she is not, there must be oxygen enough left for we, us and co., even if we should have to go after it to the bottom of the ravines, where, by its gravity, it must have accumulated! So much the better! we shall not have to climb those thundering mountains!"
So saying, he jumped up and began to gaze with considerable interest on the lunar disc, which just then was glittering with dazzling brightness.
"By Jove!" he exclaimed at length; "it must be pretty hot up there!"
"I should think so," observed the Captain; "especially when you remember that the day up there lasts 360 hours!"
"Yes," observed Barbican, "but remember on the other hand that the nights are just as long, and, as the heat escapes by radiation, the mean temperature cannot be much greater than that of interplanetary space."
"A high old place for living in!" cried Ardan. "No matter! I wish we were there now! Wouldn't it be jolly, dear boys, to have old Mother Earth for our Moon, to see her always on our sky, never rising, never setting, never undergoing any change except from New Earth to Last Quarter! Would not it be fun to trace the shape of our great Oceans and Continents, and to say: 'there is the Mediterranean! there is China! there is the gulf of Mexico! there is the white line of the Rocky Mountains where old Marston is watching for us with his big telescope!' Then we should see every line, and brightness, and shadow fade away by degrees, as she came nearer and nearer to the Sun, until at last she sat completely lost in his dazzling rays! But—by the way—Barbican, are there any eclipses in the Moon?"
"O yes; solar eclipses" replied Barbican, "must always occur whenever the centres of the three heavenly bodies are in the same line, the Earth occupying the middle place. However, such eclipses must always be annular, as the Earth, projected like a screen on the solar disc, allows more than half of the Sun to be still visible."