"Let"s see," asked Ardan, "who was Fourier, and who was Pouillet?"
"Baron Fourier, of the French Academy, wrote a famous treatise on _Heat_, which I remember reading twenty years ago in Penington"s book store," promptly responded the Captain; "Pouillet was an eminent professor of Physics at the Sorbonne, where he died, last year, I think."
"Thank you, Captain," said Ardan; "the cold does not injure your memory, though it is decidedly on the advance. See how thick the ice is already on the window panes! Let it only keep on and we shall soon have our breaths falling around us in flakes of snow."
"Let us prepare a thermometer," said Barbican, who had already set himself to work in a business-like manner.
A thermometer of the usual kind, as may be readily supposed, would be of no use whatever in the experiment that was now about to be made. In an ordinary thermometer Mercury freezes hard when exposed to a temperature of 40 below zero. But Barbican had provided himself with a _Minimum_, _self-recording_ thermometer, of a peculiar nature, invented by Wolferdin, a friend of Arago"s, which could correctly register exceedingly low degrees of temperature. Before beginning the experiment, this instrument was tested by comparison with one of the usual kind, and then Barbican hesitated a few moments regarding the best means of employing it.
"How shall we start this experiment?" asked the Captain.
"Nothing simpler," answered Ardan, always ready to reply; "you just open your windows, and fling out your thermometer. It follows your Projectile, as a calf follows her mother. In a quarter of an hour you put out your hand--"
"Put out your hand!" interrupted Barbican.
"Put out your hand--" continued Ardan, quietly.
"You do nothing of the kind," again interrupted Barbican; "that is, unless you prefer, instead of a hand, to pull back a frozen stump, shapeless, colorless and lifeless!"
"I prefer a hand," said Ardan, surprised and interested.
"Yes," continued Barbican, "the instant your hand left the Projectile, it would experience the same terrible sensations as is produced by cauterizing it with an iron bar white hot. For heat, whether rushing rapidly out of our bodies or rapidly entering them, is identically the same force and does the same amount of damage. Besides I am by no means certain that we are still followed by the objects that we flung out of the Projectile."
"Why not?" asked M"Nicholl; "we saw them all outside not long ago."
"But we can"t see them outside now," answered Barbican; "that may be accounted for, I know, by the darkness, but it may be also by the fact of their not being there at all. In a case like this, we can"t rely on uncertainties. Therefore, to make sure of not losing our thermometer, we shall fasten it with a string and easily pull it in whenever we like."
This advice being adopted, the window was opened quickly, and the instrument was thrown out at once by M"Nicholl, who held it fastened by a short stout cord so that it could be pulled in immediately. The window had hardly been open for longer than a second, yet that second had been enough to admit a terrible icy chill into the interior of the Projectile.
"Ten thousand ice-bergs!" cried Ardan, shivering all over; "it"s cold enough to freeze a white bear!"
Barbican waited quietly for half an hour; that time he considered quite long enough to enable the instrument to acquire the temperature of the interstellar s.p.a.ce. Then he gave the signal, and it was instantly pulled in.
It took him a few moments to calculate the quant.i.ty of mercury that had escaped into the little diaphragm attached to the lower part of the instrument; then he said:
"A hundred and forty degrees, centigrade, below zero!"
[Ill.u.s.tration: IT"S COLD ENOUGH TO FREEZE A WHITE BEAR.]
"Two hundred and twenty degrees, Fahrenheit, below zero!" cried M"Nicholl; "no wonder that we should feel a little chilly!"
"Pouillet is right, then," said Barbican, "and Fourier wrong."
"Another victory for Sorbonne over the Academy!" cried Ardan. "_Vive la Sorbonne!_ Not that I"m a bit proud of finding myself in the midst of a temperature so very _distingue_--though it is more than three times colder than Hayes ever felt it at Humboldt Glacier or Nevenoff at Yakoutsk. If Madame the Moon becomes as cold as this every time that her surface is withdrawn from the sunlight for fourteen days, I don"t think, boys, that her hospitality is much to hanker after!"
CHAPTER XV.
GLIMPSES AT THE INVISIBLE.
In spite of the dreadful condition in which the three friends now found themselves, and the still more dreadful future that awaited them, it must be acknowledged that Ardan bravely kept up his spirits. And his companions were just as cheerful. Their philosophy was quite simple and perfectly intelligible. What they could bear, they bore without murmuring. When it became unbearable, they only complained, if complaining would do any good. Imprisoned in an iron shroud, flying through profound darkness into the infinite abysses of s.p.a.ce, nearly a quarter million of miles distant from all human aid, freezing with the icy cold, their little stock not only of gas but of _air_ rapidly running lower and lower, a near future of the most impenetrable obscurity looming up before them, they never once thought of wasting time in asking such useless questions as where they were going, or what fate was about to befall them. Knowing that no good could possibly result from inaction or despair, they carefully kept their wits about them, making their experiments and recording their observations as calmly and as deliberately as if they were working at home in the quiet retirement of their own cabinets.
Any other course of action, however, would have been perfectly absurd on their part, and this no one knew better than themselves. Even if desirous to act otherwise, what could they have done? As powerless over the Projectile as a baby over a locomotive, they could neither clap brakes to its movement nor switch off its direction. A sailor can turn his ship"s head at pleasure; an aeronaut has little trouble, by means of his ballast and his throttle-valve, in giving a vertical movement to his balloon. But nothing of this kind could our travellers attempt. No helm, or ballast, or throttle-valve could avail them now. Nothing in the world could be done to prevent things from following their own course to the bitter end.
If these three men would permit themselves to hazard an expression at all on the subject, which they didn"t, each could have done it by his own favorite motto, so admirably expressive of his individual nature.
"_Donnez tete baissee!_" (Go it baldheaded!) showed Ardan"s uncalculating impetuosity and his Celtic blood. "_Fata quocunque vocant!_" (To its logical consequence!) revealed Barbican"s imperturbable stoicism, culture hardening rather than loosening the original British phlegm. Whilst M"Nicholl"s "Screw down the valve and let her rip!" betrayed at once his unconquerable Yankee coolness and his old experiences as a Western steamboat captain.
Where were they now, at eight o"clock in the morning of the day called in America the sixth of December? Near the Moon, very certainly; near enough, in fact, for them to perceive easily in the dark the great round screen which she formed between themselves and the Projectile on one side, and the Earth, Sun, and stars on the other. But as to the exact distance at which she lay from them--they had no possible means of calculating it. The Projectile, impelled and maintained by forces inexplicable and even incomprehensible, had come within less than thirty miles from the Moon"s north pole. But during those two hours of immersion in the dark shadow, had this distance been increased or diminished? There was evidently no stand-point whereby to estimate either the Projectile"s direction or its velocity. Perhaps, moving rapidly away from the Moon, it would be soon out of her shadow altogether. Perhaps, on the contrary, gradually approaching her surface, it might come into contact at any moment with some sharp invisible peak of the Lunar mountains--a catastrophe sure to put a sudden end to the trip, and the travellers too.
An excited discussion on this subject soon sprang up, in which all naturally took part. Ardan"s imagination as usual getting the better of his reason, he maintained very warmly that the Projectile, caught and retained by the Moon"s attraction, could not help falling on her surface, just as an aerolite cannot help falling on our Earth.
"Softly, dear boy, softly," replied Barbican; "aerolites _can_ help falling on the Earth, and the proof is, that few of them _do_ fall--most of them don"t. Therefore, even granting that we had already a.s.sumed the nature of an aerolite, it does not necessarily follow that we should fall on the Moon."
"But," objected Ardan, "if we approach only near enough, I don"t see how we can help--"
"You don"t see, it may be," said Barbican, "but you can see, if you only reflect a moment. Have you not often seen the November meteors, for instance, streaking the skies, thousands at a time?"
"Yes; on several occasions I was so fortunate."
"Well, did you ever see any of them strike the Earth"s surface?" asked Barbican.
"I can"t say I ever did," was the candid reply, "but--"
"Well, these shooting stars," continued Barbican, "or rather these wandering particles of matter, shine only from being inflamed by the friction of the atmosphere. Therefore they can never be at a greater distance from the Earth than 30 or 40 miles at furthest, and yet they seldom fall on it. So with our Projectile. It may go very close to the Moon without falling into it."
"But our roving Projectile must pull up somewhere in the long run,"
replied Ardan, "and I should like to know where that somewhere can be, if not in the Moon."
"Softly again, dear boy," said Barbican; "how do you know that our Projectile must pull up somewhere?"
"It"s self-evident," replied Ardan; "it can"t keep moving for ever."
"Whether it can or it can"t depends altogether on which one of two mathematical curves it has followed in describing its course. According to the velocity with which it was endowed at a certain moment, it must follow either the one or the other; but this velocity I do not consider myself just now able to calculate."
"Exactly so," chimed in M"Nicholl; "it must describe and keep on describing either a parabola or a hyperbola."
"Precisely," said Barbican; "at a certain velocity it would take a parabolic curve; with a velocity considerably greater it should describe a hyperbolic curve."
"I always did like nice corpulent words," said Ardan, trying to laugh; "bloated and unwieldy, they express in a neat handy way exactly what you mean. Of course, I know all about the high--high--those high curves, and those low curves. No matter. Explain them to me all the same. Consider me most deplorably ignorant on the nature of these curves."
"Well," said the Captain, a little b.u.mptiously, "a parabola is a curve of the second order, formed by the intersection of a cone by a plane parallel to one of its sides."
"You don"t say so!" cried Ardan, with mouth agape. "Do tell!"
"It is pretty nearly the path taken by a sh.e.l.l shot from a mortar."