"Well," continued the Frenchman, "suppose the comet of 1861 influenced the Earth by an attraction superior to the Sun's. What would be the consequence? Would not the Earth follow the attracting body, become its satellite, and thus at last be dragged off to such a distance that the Sun's rays could no longer excite heat on her surface?" "Well, that might possibly occur," said Barbican slowly, "but even then I question if the consequences would be so terrible as you seem to apprehend." "Why not?" "Because the cold and the heat might still manage to be nearly equalized on our globe. It has been calculated that, had the Earth been carried off by the comet of '61, when arrived at her greatest distance, she would have experienced a temperature hardly sixteen times greater than the heat we receive from the Moon, which, as everybody knows, produces no appreciable effect, even when concentrated to a focus by the most powerful lenses." "Well then," exclaimed Ardan, "at such a temperature--" "Wait a moment," replied Barbican. "Have you never heard of the principle of compensation? Listen to another calculation. Had the Earth been dragged along with the comet, it has been calculated that at her perihelion, or nearest point to the Sun, she would have to endure a heat 28,000 times greater than our mean summer temperature. But this heat, fully capable of turning the rocks into glass and the oceans into vapor, before proceeding to such extremity, must have first formed a thick interposing ring of clouds, and thus considerably modified the excessive temperature. Therefore, between the extreme cold of the aphelion and the excessive heat of the perihelion, by the great law of compensation, it is probable that the mean temperature would be tolerably endurable." "At how many degrees is the temperature of the interplanetary space estimated?" asked M'Nicholl. "Some time ago," replied Barbican, "this temperature was considered to be very low indeed--millions and millions of degrees below zero. But Fourrier of Auxerre, a distinguished member of the _Academie des Sciences_, whose _Memoires_ on the temperature of the Planetary spaces appeared about 1827, reduced these figures to considerably diminished proportions. According to his careful estimation, the temperature of space is not much lower than 70 or 80 degrees Fahr. below zero." "No more?" asked Ardan. "No more," answered Barbican, "though I must acknowledge we have only his word for it, as the _Memoire_ in which he had recorded all the elements of that important determination, has been lost somewhere, and is no longer to be found."