round the moon-第22部分

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heat；　like　the　Indians　of　the　Pampas！　now　plunged　into　profound
darkness；　amid　the　cold；　like　the　Esquimaux　of　the　north　pole。
No；　indeed！　we　have　no　right　to　complain；　nature　does　wonders　in
our　honor。〃

〃But；〃　asked　Nicholl；　〃what　is　the　temperature　outside？〃

〃Exactly　that　of　the　planetary　space；〃　replied　Barbicane。

〃Then；〃　continued　Michel　Ardan；　〃would　not　this　be　the　time　to
make　the　experiment　which　we　dared　not　attempt　when　we　were
drowned　in　the　sun's　rays？

〃It　is　now　or　never；〃　replied　Barbicane；　〃for　we　are　in　a　good
position　to　verify　the　temperature　of　space；　and　see　if　Fourier
or　Pouillet's　calculations　are　exact。〃

〃In　any　case　it　is　cold；〃　said　Michel。　　〃See！　the　steam　of　the
interior　is　condensing　on　the　glasses　of　the　scuttles。　　If　the　fall
continues；　the　vapor　of　our　breath　will　fall　in　snow　around　us。〃

〃Let　us　prepare　a　thermometer；〃　said　Barbicane。

We　may　imagine　that　an　ordinary　thermometer　would　afford　no
result　under　the　circumstances　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　passing　through　an　atmosphere　of　the
slightest　density；　these　objects　will　be　retarded。　　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　quantity　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　space。　　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　space。　　Instead　of　asking　where　they　were　going；
they　passed　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　ship　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　passed　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　shine　when　they
are　heated　by　gliding　over　the　atmospheric　layers。　　Now；　if
they　enter　the　atmosphere；　they　pass　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　space？〃

〃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
assume　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　constitutes　two　branches　separated　one　from　the　other；
both　tending　indefinitely　in　the　two　directions。〃

〃Is　it　possible！〃　exclaimed　Michel　Ardan　in　a　serious　tone；　as
if　they　had　told　him　of　some　serious　event。　　〃What　I　particularly
like　in　your　definition　of　the　hyperbola　（I　was　going　to　say
hyperblague）　is　that　it　is　still　more　obscure　than　the　word　you
pretend　to　define。〃

Nicholl　and　Barbicane　cared　little　for　Michel　Ardan's　fun。
They　were　deep　in　a　scientific　discussion。　　What　curve　would
the　projectile　follow？　was　their　hobby。　　One　maintained　the
hyperbola；　the　other　the　parabola。　　They　gave　each　other　reasons
bristling　with　_x_。　　Their　arguments　were　couched　in　language
which　made　Michel　jump。　　The　discussion　was　hot；　and　neither
would　give　up　his　chosen　curve　to　his　adversary。

This　scientific　dispute　lasted　so　long　that　it　made　Michel
very　impatient。

〃Now；　gentlemen　cosines；　will　you　cease　to　throw　parabolas　and
hyperbolas　at　each　other's　heads？　　I　want　to　understand　the　only
interesting　question　in　the　whole　affair。　　We　shall　follow　one
or　the　other　of　these　curves？　　Good。　　But　where　will　they　lead
us　to？〃

〃Nowhere；〃　replied　Nicholl。

〃How；　nowhere？〃

〃Evidently；〃　said　Barbicane；　〃they　are　open　curves；　which　may　be
prolonged　ind