Instructive Conversation

: All Around The Moon

On the fourth of December, the Projectile chronometers marked five

o'clock in the morning, just as the travellers woke up from a pleasant

slumber. They had now been 54 hours on their journey. As to lapse of

time, they had passed not much more than half of the number of hours

during which their trip was to last; but, as to lapse of space, they

had already accomplished very nearly the seven-tenths of their passage.

This ifference between time and distance was due to the regular

retardation of their velocity.



They looked at the earth through the floor-light, but it was little more

than visible--a black spot drowned in the solar rays. No longer any sign

of a crescent, no longer any sign of ashy light. Next day, towards

midnight, the Earth was to be new, at the precise moment when the Moon

was to be full. Overhead, they could see the Queen of Night coming

nearer and nearer to the line followed by the Projectile, and evidently

approaching the point where both should meet at the appointed moment.

All around, the black vault of heaven was dotted with luminous points

which seemed to move somewhat, though, of course, in their extreme

distance their relative size underwent no change. The Sun and the stars

looked exactly as they had appeared when observed from the Earth. The

Moon indeed had become considerably enlarged in size, but the

travellers' telescopes were still too weak to enable them to make any

important observation regarding the nature of her surface, or that might

determine her topographical or geological features.



Naturally, therefore, the time slipped away in endless conversation. The

Moon, of course, was the chief topic. Each one contributed his share of

peculiar information, or peculiar ignorance, as the case might be.

Barbican and M'Nicholl always treated the subject gravely, as became

learned scientists, but Ardan preferred to look on things with the eye

of fancy. The Projectile, its situation, its direction, the incidents

possible to occur, the precautions necessary to take in order to break

the fall on the Moon's surface--these and many other subjects furnished

endless food for constant debate and inexhaustible conjectures.



For instance, at breakfast that morning, a question of Ardan's regarding

the Projectile drew from Barbican an answer curious enough to be

reported.



"Suppose, on the night that we were shot up from Stony Hill," said

Ardan, "suppose the Projectile had encountered some obstacle powerful

enough to stop it--what would be the consequence of the sudden halt?"



"But," replied Barbican, "I don't understand what obstacle it could have

met powerful enough to stop it."



"Suppose some obstacle, for the sake of argument," said Ardan.



"Suppose what can't be supposed," replied the matter-of-fact Barbican,

"what cannot possibly be supposed, unless indeed the original impulse

proved too weak. In that case, the velocity would have decreased by

degrees, but the Projectile itself would not have suddenly stopped."



"Suppose it had struck against some body in space."



"What body, for instance?"



"Well, that enormous bolide which we met."



"Oh!" hastily observed the Captain, "the Projectile would have been

dashed into a thousand pieces and we along with it."



"Better than that," observed Barbican; "we should have been burned

alive."



"Burned alive!" laughed Ardan. "What a pity we missed so interesting an

experiment! How I should have liked to find out how it felt!"



"You would not have much time to record your observations, friend

Michael, I assure you," observed Barbican. "The case is plain enough.

Heat and motion are convertible terms. What do we mean by heating water?

Simply giving increased, in fact, violent motion to its molecules."



"Well!" exclaimed the Frenchman, "that's an ingenious theory any how!"



"Not only ingenious but correct, my dear friend, for it completely

explains all the phenomena of caloric. Heat is nothing but molecular

movement, the violent oscillation of the particles of a body. When you

apply the brakes to the train, the train stops. But what has become of

its motion? It turns into heat and makes the brakes hot. Why do people

grease the axles? To hinder them from getting too hot, which they

assuredly would become if friction was allowed to obstruct the motion.

You understand, don't you?"



"Don't I though?" replied Ardan, apparently in earnest. "Let me show you

how thoroughly. When I have been running hard and long, I feel myself

perspiring like a bull and hot as a furnace. Why am I then forced to

stop? Simply because my motion has been transformed into heat! Of

course, I understand all about it!"



Barbican smiled a moment at this comical illustration of his theory and

then went on:



"Accordingly, in case of a collision it would have been all over

instantly with our Projectile. You have seen what becomes of the bullet

that strikes the iron target. It is flattened out of all shape;

sometimes it is even melted into a thin film. Its motion has been turned

into heat. Therefore, I maintain that if our Projectile had struck that

bolide, its velocity, suddenly checked, would have given rise to a heat

capable of completely volatilizing it in less than a second."



"Not a doubt of it!" said the Captain. "President," he added after a

moment, "haven't they calculated what would be the result, if the Earth

were suddenly brought to a stand-still in her journey, through her

orbit?"



"It has been calculated," answered Barbican, "that in such a case so

much heat would be developed as would instantly reduce her to vapor."



"Hm!" exclaimed Ardan; "a remarkably simple way for putting an end to

the world!"



"And supposing the Earth to fall into the Sun?" asked the Captain.



"Such a fall," answered Barbican, "according to the calculations of

Tyndall and Thomson, would develop an amount of heat equal to that

produced by sixteen hundred globes of burning coal, each globe equal in

size to the earth itself. Furthermore such a fall would supply the Sun

with at least as much heat as he expends in a hundred years!"



"A hundred years! Good! Nothing like accuracy!" cried Ardan. "Such

infallible calculators as Messrs. Tyndall and Thomson I can easily

excuse for any airs they may give themselves. They must be of an order

much higher than that of ordinary mortals like us!"



"I would not answer myself for the accuracy of such intricate problems,"

quietly observed Barbican; "but there is no doubt whatever regarding one

fact: motion suddenly interrupted always develops heat. And this has

given rise to another theory regarding the maintenance of the Sun's

temperature at a constant point. An incessant rain of bolides falling on

his surface compensates sufficiently for the heat that he is

continually giving forth. It has been calculated--"



"Good Lord deliver us!" cried Ardan, putting his hands to his ears:

"here comes Tyndall and Thomson again!"



--"It has been calculated," continued Barbican, not heeding the

interruption, "that the shock of every bolide drawn to the Sun's surface

by gravity, must produce there an amount of heat equal to that of the

combustion of four thousand blocks of coal, each the same size as the

falling bolide."



"I'll wager another cent that our bold savants calculated the heat of

the Sun himself," cried Ardan, with an incredulous laugh.



"That is precisely what they have done," answered Barbican referring to

his memorandum book; "the heat emitted by the Sun," he continued, "is

exactly that which would be produced by the combustion of a layer of

coal enveloping the Sun's surface, like an atmosphere, 17 miles in

thickness."



"Well done! and such heat would be capable of--?"



"Of melting in an hour a stratum of ice 2400 feet thick, or, according

to another calculation, of raising a globe of ice-cold water, 3 times

the size of our Earth, to the boiling point in an hour."



"Why not calculate the exact fraction of a second it would take to cook

a couple of eggs?" laughed Ardan. "I should as soon believe in one

calculation as in the other.--But--by the by--why does not such extreme

heat cook us all up like so many beefsteaks?"



"For two very good and sufficient reasons," answered Barbican. "In the

first place, the terrestrial atmosphere absorbs the 4/10 of the solar

heat. In the second, the quantity of solar heat intercepted by the Earth

is only about the two billionth part of all that is radiated."



"How fortunate to have such a handy thing as an atmosphere around us,"

cried the Frenchman; "it not only enables us to breathe, but it actually

keeps us from sizzling up like griskins."



"Yes," said the Captain, "but unfortunately we can't say so much for the

Moon."



"Oh pshaw!" cried Ardan, always full of confidence. "It's all right

there too! The Moon is either inhabited or she is not. If she is, the

inhabitants must breathe. If she is not, there must be oxygen enough

left for we, us and co., even if we should have to go after it to the

bottom of the ravines, where, by its gravity, it must have accumulated!

So much the better! we shall not have to climb those thundering

mountains!"



So saying, he jumped up and began to gaze with considerable interest on

the lunar disc, which just then was glittering with dazzling brightness.



"By Jove!" he exclaimed at length; "it must be pretty hot up there!"



"I should think so," observed the Captain; "especially when you remember

that the day up there lasts 360 hours!"



"Yes," observed Barbican, "but remember on the other hand that the

nights are just as long, and, as the heat escapes by radiation, the mean

temperature cannot be much greater than that of interplanetary space."



"A high old place for living in!" cried Ardan. "No matter! I wish we

were there now! Wouldn't it be jolly, dear boys, to have old Mother

Earth for our Moon, to see her always on our sky, never rising, never

setting, never undergoing any change except from New Earth to Last

Quarter! Would not it be fun to trace the shape of our great Oceans and

Continents, and to say: 'there is the Mediterranean! there is China!

there is the gulf of Mexico! there is the white line of the Rocky

Mountains where old Marston is watching for us with his big telescope!'

Then we should see every line, and brightness, and shadow fade away by

degrees, as she came nearer and nearer to the Sun, until at last she sat

completely lost in his dazzling rays! But--by the way--Barbican, are

there any eclipses in the Moon?"



"O yes; solar eclipses" replied Barbican, "must always occur whenever

the centres of the three heavenly bodies are in the same line, the Earth

occupying the middle place. However, such eclipses must always be

annular, as the Earth, projected like a screen on the solar disc, allows

more than half of the Sun to be still visible."



"How is that?" asked M'Nicholl, "no total eclipses in the Moon? Surely

the cone of the Earth's shadow must extend far enough to envelop her

surface?"



"It does reach her, in one sense," replied Barbican, "but it does not in

another. Remember the great refraction of the solar rays that must be

produced by the Earth's atmosphere. It is easy to show that this

refraction prevents the Sun from ever being totally invisible. See

here!" he continued, pulling out his tablets, "Let a represent the

horizontal parallax, and b the half of the Sun's apparent diameter--"



"Ouch!" cried the Frenchman, making a wry face, "here comes Mr. x

square riding to the mischief on a pair of double zeros again! Talk

English, or Yankee, or Dutch, or Greek, and I'm your man! Even a little

Arabic I can digest! But hang me, if I can endure your Algebra!"



"Well then, talking Yankee," replied Barbican with a smile, "the mean

distance of the Moon from the Earth being sixty terrestrial radii, the

length of the conic shadow, in consequence of atmospheric refraction, is

reduced to less than forty-two radii. Consequently, at the moment of an

eclipse, the Moon is far beyond the reach of the real shadow, so that

she can see not only the border rays of the Sun, but even those

proceeding from his very centre."



"Oh then," cried Ardan with a loud laugh, "we have an eclipse of the Sun

at the moment when the Sun is quite visible! Isn't that very like a

bull, Mr. Philosopher Barbican?"



"Yet it is perfectly true notwithstanding," answered Barbican. "At such

a moment the Sun is not eclipsed, because we can see him: and then again

he is eclipsed because we see him only by means of a few of his rays,

and even these have lost nearly all their brightness in their passage

through the terrestrial atmosphere!"



"Barbican is right, friend Michael," observed the Captain slowly: "the

same phenomenon occurs on earth every morning at sunrise, when

refraction shows us



'the Sun new ris'n

Looking through the horizontal misty air,

Shorn of his beams.'"



"He must be right," said Ardan, who, to do him justice, though quick at

seeing a reason, was quicker to acknowledge its justice: "yes, he must

be right, because I begin to understand at last very clearly what he

really meant. However, we can judge for ourselves when we get

there.--But, apropos of nothing, tell me, Barbican, what do you think of

the Moon being an ancient comet, which had come so far within the sphere

of the Earth's attraction as to be kept there and turned into a

satellite?"



"Well, that is an original idea!" said Barbican with a smile.



"My ideas generally are of that category," observed Ardan with an

affectation of dry pomposity.



"Not this time, however, friend Michael," observed M'Nicholl.



"Oh! I'm a plagiarist, am I?" asked the Frenchman, pretending to be

irritated.



"Well, something very like it," observed M'Nicholl quietly. "Apollonius

Rhodius, as I read one evening in the Philadelphia Library, speaks of

the Arcadians of Greece having a tradition that their ancestors were so

ancient that they inhabited the Earth long before the Moon had ever

become our satellite. They therefore called them [Greek: Proselenoi]

or Ante-lunarians. Now starting with some such wild notion as this,

certain scientists have looked on the Moon as an ancient comet brought

close enough to the Earth to be retained in its orbit by terrestrial

attraction."



"Why may not there be something plausible in such a hypothesis?" asked

Ardan with some curiosity.



"There is nothing whatever in it," replied Barbican decidedly: "a simple

proof is the fact that the Moon does not retain the slightest trace of

the vaporous envelope by which comets are always surrounded."



"Lost her tail you mean," said Ardan. "Pooh! Easy to account for that!

It might have got cut off by coming too close to the Sun!"



"It might, friend Michael, but an amputation by such means is not very

likely."



"No? Why not?"



"Because--because--By Jove, I can't say, because I don't know," cried

Barbican with a quiet smile on his countenance.



"Oh what a lot of volumes," cried Ardan, "could be made out of what we

don't know!"



"At present, for instance," observed M'Nicholl, "I don't know what

o'clock it is."



"Three o'clock!" said Barbican, glancing at his chronometer.



"No!" cried Ardan in surprise. "Bless us! How rapidly the time passes

when we are engaged in scientific conversation! Ouf! I'm getting

decidedly too learned! I feel as if I had swallowed a library!"



"I feel," observed M'Nicholl, "as if I had been listening to a lecture

on Astronomy in the Star course."



"Better stir around a little more," said the Frenchman; "fatigue of body

is the best antidote to such severe mental labor as ours. I'll run up

the ladder a bit." So saying, he paid another visit to the upper portion

of the Projectile and remained there awhile whistling Malbrouk, whilst

his companions amused themselves in looking through the floor window.



Ardan was coming down the ladder, when his whistling was cut short by a

sudden exclamation of surprise.



"What's the matter?" asked Barbican quickly, as he looked up and saw the

Frenchman pointing to something outside the Projectile.



Approaching the window, Barbican saw with much surprise a sort of

flattened bag floating in space and only a few yards off. It seemed

perfectly motionless, and, consequently, the travellers knew that it

must be animated by the same ascensional movement as themselves.



"What on earth can such a consarn be, Barbican?" asked Ardan, who every

now and then liked to ventilate his stock of American slang. "Is it one

of those particles of meteoric matter you were speaking of just now,

caught within the sphere of our Projectile's attraction and accompanying

us to the Moon?"



"What I am surprised at," observed the Captain, "is that though the

specific gravity of that body is far inferior to that of our Projectile,

it moves with exactly the same velocity."



"Captain," said Barbican, after a moment's reflection, "I know no more

what that object is than you do, but I can understand very well why it

keeps abreast with the Projectile."



"Very well then, why?"



"Because, my dear Captain, we are moving through a vacuum, and because

all bodies fall or move--the same thing--with equal velocity through a

vacuum, no matter what may be their shape or their specific gravity. It

is the air alone that makes a difference of weight. Produce an

artificial vacuum in a glass tube and you will see that all objects

whatever falling through, whether bits of feather or grains of shot,

move with precisely the same rapidity. Up here, in space, like cause and

like effect."



"Correct," assented M'Nicholl. "Everything therefore that we shall throw

out of the Projectile is bound to accompany us to the Moon."



"Well, we were smart!" cried Ardan suddenly.



"How so, friend Michael?" asked Barbican.



"Why not have packed the Projectile with ever so many useful objects,

books, instruments, tools, et cetera, and fling them out into space once

we were fairly started! They would have all followed us safely! Nothing

would have been lost! And--now I think on it--why not fling ourselves

out through the window? Shouldn't we be as safe out there as that

bolide? What fun it would be to feel ourselves sustained and upborne in

the ether, more highly favored even than the birds, who must keep on

flapping their wings continually to prevent themselves from falling!"



"Very true, my dear boy," observed Barbican; "but how could we breathe?"



"It's a fact," exclaimed the Frenchman. "Hang the air for spoiling our

fun! So we must remain shut up in our Projectile?"



"Not a doubt of it!"



--"Oh Thunder!" roared Ardan, suddenly striking his forehead.



"What ails you?" asked the Captain, somewhat surprised.



"Now I know what that bolide of ours is! Why didn't we think of it

before? It is no asteroid! It is no particle of meteoric matter! Nor is

it a piece of a shattered planet!"



"What is it then?" asked both of his companions in one voice.






"It is nothing more or less than the body of the dog that we threw out

yesterday!"



So in fact it was. That shapeless, unrecognizable mass, melted,

expunged, flat as a bladder under an unexhausted receiver, drained of

its air, was poor Satellite's body, flying like a rocket through space,

and rising higher and higher in close company with the rapidly ascending

Projectile!