"Well," resumed Michel, "it is well known that in 1861 the earth went through the tail of a comet. Now suppose there was a comet with a power of attraction greater than that of the sun, the terrestrial globe might make a curve towards the wandering star, and the earth would become its satellite, and would be dragged away to such a distance that the rays of the sun would have no action on its surface." "That might happen certainly," answered Barbicane, "but the consequences would not be so redoubtable as you would suppose." "How so?" "Because heat and cold would still be pretty well balanced upon our globe. It has been calculated that if the earth had been carried away by the comet of 1861, it would only have felt, when at its greatest distance from the sun, a heat sixteen times greater than that sent to us by the moon--a heat which, when focussed by the strongest lens, produces no appreciable effect." "Well?" said Michel. "Wait a little," answered Barbicane. "It has been calculated that at its perihelion, when nearest to the sun, the earth would have borne a heat equal to 28,000 times that of summer. But this heat, capable of vitrifying terrestrial matters, and of evaporating water, would have formed a thick circle of clouds which would have lessened the excessive heat, hence there would be compensation between the cold of the aphelion and the heat of the perihelion, and an average probably supportable." "At what number of degrees do they estimate the temperature of the planetary space?" "Formerly," answered Barbicane, "it was believed that this temperature was exceedingly low. By calculating its thermometric diminution it was fixed at millions of degrees below zero. It was Fourier, one of Michel's countrymen, an illustrious _savant_ of the _Académie des Sciences_, who reduced these numbers to a juster estimation. According to him, the temperature of space does not get lower than 60° Centigrade." Michel whistled. "It is about the temperature of the polar regions," answered Barbicane, "at Melville Island or Fort Reliance--about 56° Centigrade below zero." "It remains to be proved," said Nicholl, "that Fourier was not mistaken in his calculations. If I am not mistaken, another Frenchman, M. Pouillet, estimates the temperature of space at 160° below zero. We shall be able to verify that." "Not now," answered Barbicane, "for the solar rays striking directly upon our thermometer would give us, on the contrary, a very elevated temperature. But when we get upon the moon, during the nights, a fortnight long, which each of its faces endures alternately, we shall have leisure to make the experiment, for our satellite moves in the void." "What do you mean by the void?" asked Michel; "is it absolute void?" "It is absolutely void of air." "Is there nothing in its place?" "Yes, ether," answered Barbicane. "Ah! and what is ether?"