It is generally admitted that the invisible hemisphere of the moon is, by its constitution, absolutely similar to the visible hemisphere. One-seventh of it is seen in those movements of libration Barbicane spoke of. Now upon the surface seen there were only plains and mountains, amphitheatres and craters, like those on the maps. They could there imagine the same arid and dead nature. And yet, supposing the atmosphere to have taken refuge upon that face? Suppose that with the air water had given life to these regenerated continents? Suppose that vegetation still persists there? Suppose that animals people these continents and seas? Suppose that man still lives under those conditions of habitability? How many questions there were it would have been interesting to solve! What solutions might have been drawn from the contemplation of that hemisphere! What delight it would have been to glance at that world which no human eye has seen!
The disappointment of the travellers in the midst of this darkness may be imagined. All observation of the lunar disc was prevented. The constellations alone were visible, and it must be acknowledged that no astronomers, neither Faye, Chacornac, nor the Secchi, had ever been in such favourable conditions to observe them.
In fact, nothing could equal the splendour of this starry world, bathed in limpid ether. Diamonds set in the celestial vault threw out superb flames. One look could take in the firmament from the Southern Cross to the North Star, those two constellations which will in 12,000 years, on account of the succession of equinoxes, resign their roles of polar stars, the one to Canopus in the southern hemisphere, the other to Wega in the northern. Imagination lost itself in this sublime infinitude, amidst which the projectile was moving like a new star created by the hand of man. From natural causes these constellations shone with a soft lustre; they did not twinkle because there was no atmosphere to intervene with its strata unequally dense, and of different degrees of humidity, which causes this scintillation.
The travellers long watched the constellated firmament, upon which the vast screen of the moon made an enormous black hole. But a painful sensation at length drew them from their contemplation. This was an intense cold, which soon covered the glasses of the port-lights with a thick coating of ice. The sun no longer warmed the projectile with his rays, and it gradually lost the heat stored up in its walls. This heat was by radiation rapidly evaporated into space, and a considerable lowering of the temperature was the result. The interior humidity was changed into ice by contact with the windowpanes, and prevented all observation.
Nicholl, consulting the thermometer, said that it had fallen to 17° (centigrade) below zero (1° Fahr). Therefore, notwithstanding every reason for being economical, Barbicane was obliged to seek heat as well as light from gas. The low temperature of the bullet was no longer bearable. Its occupants would have been frozen to death.
“We will not complain about the monotony of the journey,” said Michel Ardan. “What variety we have had, in temperature at all events! At times we have been blinded with light, and saturated with heat like the Indians of the Pampas! Now we are plunged into profound darkness amidst boreal cold, like the Eskimo of the pole! No, indeed! We have no right to complain, and Nature has done many things in our honour!”
“But,” asked Nicholl, “what is the exterior temperature?”
“Precisely that of planetary space,” answered Barbicane.
“Then,” resumed Michel Ardan, “would not this be an opportunity for making that experiment we could not attempt when we were bathed in the solar rays?”
“Now or never,” answered Barbicane, “for we are usefully situated in order to verify the temperature of space, and see whether the calculations of Fourier or Pouillet are correct.”
“Anyway it is cold enough,” said Michel. “Look at the interior humidity condensing on the port-lights. If this fall continues the vapour of our respiration will fall around us in snow.”
“Let us get a thermometer,” said Barbicane.
It will be readily seen that an ordinary thermometer would have given no result under the circumstances in which it was going to be exposed. The mercury would have frozen in its cup, for it does not keep liquid below 44° below zero. But Barbicane had provided himself with a spirit thermometer, on the Walferdin system, which gives the minima of excessively low temperature.
Before beginning the experiment this instrument was compared with an ordinary thermometer, and Barbicane prepared to employ it.
“How shall we manage it?” asked Nicholl.
“Nothing is easier,” answered Michel Ardan, who was never at a loss. “Open the port-light rapidly, throw out the instrument; it will follow the projectile with exemplary docility; a quarter of an hour after take it in.”
“With your hand?” asked Barbicane.
“With my hand,” answered Michel.
“Well, then, my friend, do not try it,” said Barbicane, “for the hand you draw back will be only a stump, frozen and deformed by the frightful cold.”
“Really?”
“You would feel the sensation of a terrible burn, like one made with a red-hot iron, for the same thing happens when heat is brutally abstracted from our body as when it is inserted. Besides, I am not sure that objects thrown out still follow us.”
“Why?” said Nicholl.
“Because if we are passing through any atmosphere, however slightly dense, these objects will be delayed. Now the darkness prevents us verifying whether they still float around us. Therefore, in order not to risk our thermometer, we will tie something to it, and so easily pull it back into the interior.”
Barbicane’s advice was followed. Nicholl threw the instrument out of the rapidly-opened port-light, holding it by a very short cord, so that it could be rapidly drawn in. The window was only open one second, and yet that one second was enough to allow the interior of the projectile to become frightfully cold.
“Mille diables!” cried Michel Ardan, “it is cold enough here to freeze white bears!”
Barbicane let half-an-hour go by, more than sufficient time to
