From the Earth to the Moon Part 44

We may imagine that an ordinary thermometer would afford no result under the circ.u.mstances in which this instrument was to be exposed. The mercury would have been frozen in its ball, as below 42@ Fahrenheit below zero it is no longer liquid.

But Barbicane had furnished himself with a spirit thermometer on Wafferdin's system, which gives the minima of excessively low temperatures.

Before beginning the experiment, this instrument was compared with an ordinary one, and then Barbicane prepared to use it.

"How shall we set about it?" asked Nicholl.

"Nothing is easier," replied Michel Ardan, who was never at a loss.

"We open the scuttle rapidly; throw out the instrument; it follows the projectile with exemplary docility; and a quarter of an hour after, draw it in."

"With the hand?" asked Barbicane.

"With the hand," replied Michel.

"Well, then, my friend, do not expose yourself," answered Barbicane, "for the hand that you draw in again will be nothing but a stump frozen and deformed by the frightful cold."

"Really!"

"You will feel as if you had had a terrible burn, like that of iron at a white heat; for whether the heat leaves our bodies briskly or enters briskly, it is exactly the same thing.

Besides, I am not at all certain that the objects we have thrown out are still following us."

"Why not?" asked Nicholl.

"Because, if we are pa.s.sing through an atmosphere of the slightest density, these objects will be r.e.t.a.r.ded. Again, the darkness prevents our seeing if they still float around us.

But in order not to expose ourselves to the loss of our thermometer, we will fasten it, and we can then more easily pull it back again."

Barbicane's advice was followed. Through the scuttle rapidly opened, Nicholl threw out the instrument, which was held by a short cord, so that it might be more easily drawn up. The scuttle had not been opened more than a second, but that second had sufficed to let in a most intense cold.

"The devil!" exclaimed Michel Ardan, "it is cold enough to freeze a white bear."

Barbicane waited until half an hour had elapsed, which was more than time enough to allow the instrument to fall to the level of the surrounding temperature. Then it was rapidly pulled in.

Barbicane calculated the quant.i.ty of spirits of wine overflowed into the little vial soldered to the lower part of the instrument, and said:

"A hundred and forty degrees Centigrade [4] below zero!"

[4] 218 degrees Fahrenheit below zero.

M. Pouillet was right and Fourier wrong. That was the undoubted temperature of the starry s.p.a.ce. Such is, perhaps, that of the lunar continents, when the orb of night has lost by radiation all the heat which fifteen days of sun have poured into her.

CHAPTER XV

HYPERBOLA OR PARABOLA

We may, perhaps, be astonished to find Barbicane and his companions so little occupied with the future reserved for them in their metal prison which was bearing them through the infinity of s.p.a.ce. Instead of asking where they were going, they pa.s.sed their time making experiments, as if they had been quietly installed in their own study.

We might answer that men so strong-minded were above such anxieties-- that they did not trouble themselves about such trifles-- and that they had something else to do than to occupy their minds with the future.

The truth was that they were not masters of their projectile; they could neither check its course, nor alter its direction.

A sailor can change the head of his s.h.i.+p as he pleases; an aeronaut can give a vertical motion to his balloon. They, on the contrary, had no power over their vehicle. Every maneuver was forbidden. Hence the inclination to let things alone, or as the sailors say, "let her run."

Where did they find themselves at this moment, at eight o'clock in the morning of the day called upon the earth the 6th of December?

Very certainly in the neighborhood of the moon, and even near enough for her to look to them like an enormous black screen upon the firmament. As to the distance which separated them, it was impossible to estimate it. The projectile, held by some unaccountable force, had been within four miles of grazing the satellite's north pole.

But since entering the cone of shadow these last two hours, had the distance increased or diminished? Every point of mark was wanting by which to estimate both the direction and the speed of the projectile.

Perhaps it was rapidly leaving the disc, so that it would soon quit the pure shadow. Perhaps, again, on the other hand, it might be nearing it so much that in a short time it might strike some high point on the invisible hemisphere, which would doubtlessly have ended the journey much to the detriment of the travelers.

A discussion arose on this subject, and Michel Ardan, always ready with an explanation, gave it as his opinion that the projectile, held by the lunar attraction, would end by falling on the surface of the terrestrial globe like an aerolite.

"First of all, my friend," answered Barbicane, "every aerolite does not fall to the earth; it is only a small proportion which do so; and if we had pa.s.sed into an aerolite, it does not necessarily follow that we should ever reach the surface of the moon."

"But how if we get near enough?" replied Michel.

"Pure mistake," replied Barbicane. "Have you not seen shooting stars rush through the sky by thousands at certain seasons?"

"Yes."

"Well, these stars, or rather corpuscles, only s.h.i.+ne when they are heated by gliding over the atmospheric layers. Now, if they enter the atmosphere, they pa.s.s at least within forty miles of the earth, but they seldom fall upon it. The same with our projectile. It may approach very near to the moon, and not yet fall upon it."

"But then," asked Michel, "I shall be curious to know how our erring vehicle will act in s.p.a.ce?"

"I see but two hypotheses," replied Barbicane, after some moments' reflection.

"What are they?"

"The projectile has the choice between two mathematical curves, and it will follow one or the other according to the speed with which it is animated, and which at this moment I cannot estimate."

"Yes," said Nicholl, "it will follow either a parabola or a hyperbola."

"Just so," replied Barbicane. "With a certain speed it will a.s.sume the parabola, and with a greater the hyperbola."

"I like those grand words," exclaimed Michel Ardan; "one knows directly what they mean. And pray what is your parabola, if you please?"

"My friend," answered the captain, "the parabola is a curve of the second order, the result of the section of a cone intersected by a plane parallel to one of the sides."

"Ah! ah!" said Michel, in a satisfied tone.

"It is very nearly," continued Nicholl, "the course described by a bomb launched from a mortar."

"Perfect! And the hyperbola?"

"The hyperbola, Michel, is a curve of the second order, produced by the intersection of a conic surface and a plane parallel to its axis, and const.i.tutes two branches separated one from the other, both tending indefinitely in the two directions."