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that heat is only a modification of motion。 When water is
warmed that is to say； when heat is added to itits particles
are set in motion。〃
〃Well；〃 said michel； 〃that is an ingenious theory！〃
〃And a true one； my worthy friend； for it explains every
phenomenon of caloric。 Heat is but the motion of atoms； a
simple oscillation of the particles of a body。 When they apply
the brake to a train； the train comes to a stop； but what
becomes of the motion which it had previously possessed？ It is
transformed into heat； and the brake becomes hot。 Why do they
grease the axles of the wheels？ To prevent their heating；
because this heat would be generated by the motion which is thus
lost by transformation。〃
〃Yes； I understand；〃 replied Michel； 〃perfectly。 For example；
when I have run a long time； when I am swimming； when I am
perspiring in large drops； why am I obliged to stop？
Simply because my motion is changed into heat。〃
Barbicane could not help smiling at Michel's reply； then；
returning to his theory； said：
〃Thus； in case of a shock； it would have been with our
projectile as with a ball which falls in a burning state after
having struck the metal plate； it is its motion which is turned
into heat。 Consequently I affirm that； if our projectile had
struck the meteor； its speed thus suddenly checked would have
raised a heat great enough to turn it into vapor instantaneously。〃
〃Then；〃 asked Nicholl； 〃what would happen if the earth's motion
were to stop suddenly？〃
〃Her temperature would be raised to such a pitch；〃 said
Barbicane； 〃that she would be at once reduced to vapor。〃
〃Well；〃 said Michel； 〃that is a way of ending the earth which
will greatly simplify things。〃
〃And if the earth fell upon the sun？〃 asked Nicholl。
〃According to calculation；〃 replied Barbicane； 〃the fall would
develop a heat equal to that produced by 16；000 globes of coal；
each equal in bulk to our terrestrial globe。〃
〃Good additional heat for the sun；〃 replied Michel Ardan； 〃of
which the inhabitants of Uranus or Neptune would doubtless not
complain； they must be perished with cold on their planets。〃
〃Thus； my friends；〃 said Barbicane； 〃all motion suddenly stopped
produces heat。 And this theory allows us to infer that the heat
of the solar disc is fed by a hail of meteors falling
incessantly on its surface。 They have even calculated〃
〃Oh； dear！〃 murmured Michel； 〃the figures are coming。〃
〃They have even calculated；〃 continued the imperturbable Barbicane；
〃that the shock of each meteor on the sun ought to produce a heat
equal to that of 4；000 masses of coal of an equal bulk。〃
〃And what is the solar heat？〃 asked Michel。
〃It is equal to that produced by the combustion of a stratum of
coal surrounding the sun to a depth of forty…seven miles。〃
〃And that heat〃
〃Would be able to boil two billions nine hundred millions of
cubic myriameters ＇2＇ of water。〃
＇2＇ The myriameter is equal to rather more than 10；936
cubic yards English。
〃And it does not roast us！〃 exclaimed Michel。
〃No；〃 replied Barbicane； 〃because the terrestrial atmosphere
absorbs four…tenths of the solar heat； besides； the quantity of
heat intercepted by the earth is but a billionth part of the
entire radiation。〃
〃I see that all is for the best；〃 said Michel； 〃and that this
atmosphere is a useful invention； for it not only allows us to
breathe； but it prevents us from roasting。〃
〃Yes！〃 said Nicholl； 〃unfortunately； it will not be the same in
the moon。〃
〃Bah！〃 said Michel； always hopeful。 〃If there are inhabitants；
they must breathe。 If there are no longer any； they must have
left enough oxygen for three people； if only at the bottom of
ravines； where its own weight will cause it to accumulate； and
we will not climb the mountains； that is all。〃 And Michel；
rising； went to look at the lunar disc； which shone with
intolerable brilliancy。
〃By Jove！〃 said he； 〃it must be hot up there！〃
〃Without considering；〃 replied Nicholl； 〃that the day lasts 360 hours！〃
〃And to compensate that；〃 said Barbicane； 〃the nights have the
same length； and as heat is restored by radiation； their
temperature can only be that of the planetary space。〃
〃A pretty country； that！〃 exclaimed Michel。 〃Never mind！
I wish I was there！ Ah！ my dear comrades； it will be rather
curious to have the earth for our moon； to see it rise on the
horizon； to recognize the shape of its continents； and to say
to oneself； ‘There is America； there is Europe；' then to follow
it when it is about to lose itself in the sun's rays！ By the
bye； Barbicane； have the Selenites eclipses？〃
〃Yes； eclipses of the sun；〃 replied Barbicane； 〃when the centers
of the three orbs are on a line； the earth being in the middle。
But they are only partial； during which the earth； cast like a
screen upon the solar disc； allows the greater portion to be seen。〃
〃And why；〃 asked Nicholl； 〃is there no total eclipse？ Does not
the cone of the shadow cast by the earth extend beyond the moon？〃
〃Yes； if we do not take into consideration the refraction
produced by the terrestrial atmosphere。 No； if we take that
refraction into consideration。 Thus let be
the horizontal parallel； and _p_ the apparent semidiameter〃
〃Oh！〃 said Michel。 〃Do speak plainly； you man of algebra！〃
〃Very well； replied Barbicane； 〃in popular language the mean
distance from the moon to the earth being sixty terrestrial
radii； the length of the cone of the shadow； on account of
refraction； is reduced to less than forty…two radii。
The result is that when there are eclipses； the moon finds
itself beyond the cone of pure shadow； and that the sun sends
her its rays； not only from its edges； but also from its center。〃
〃Then；〃 said Michel； in a merry tone； 〃why are there eclipses；
when there ought not to be any？〃
〃Simply because the solar rays are weakened by this refraction；
and the atmosphere through which they pass extinguished the
greater part of them！〃
〃That reason satisfies me；〃 replied Michel。 〃Besides we shall
see when we get there。 Now； tell me； Barbicane； do you believe
that the moon is an old comet？〃
〃There's an idea！〃
〃Yes；〃 replied Michel； with an amiable swagger； 〃I have a few
ideas of that sort。〃
〃But that idea does not spring from Michel；〃 answered Nicholl。
〃Well； then； I am a plagiarist。〃
〃No doubt about it。 According to the ancients； the Arcadians
pretend that their ancestors inhabited the earth before the moon
became her satellite。 Starting from this fact； some scientific
men have seen in the moon a comet whose orbit will one day bring
it so near to the earth that it will be held there by its attraction。〃
〃Is there any truth in this hypothesis？〃 asked Michel。
〃None whatever；〃 said Barbicane； 〃and the proof is； that the
moon has preserved no trace of the gaseous envelope which always
accompanies comets。〃
〃But；〃 continued Nicholl； 〃Before becoming the earth's satellite；
could not the moon； when in her perihelion； pass so near the sun
as by evaporation to get rid of all those gaseous substances？〃
〃It is possible； friend Nicholl； but not probable。〃
〃Why not？〃
〃Because Faith I