a journey in other worlds-第32章

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flame　and　torrents　of　molten　glowing　lava；　bursting　at　intervals
or　pouring　steadily　from　several　volcanoes。　　From　this　they
concluded　they　were　again　near　an　ocean；　since　volcanoes　need　the
presence　of　a　large　body　of　water　to　provide　steam　for　their
eruptions。
　　　
With　the　rising　sun　they　found　the　scene　of　the　day　before
entirely　changed。　　They　were　over　the　shore　of　a　vast　ocean　that
extended　to　the　left　as　far　as　they　could　see；　for　the　range　of
vision　often　exceeded　the　power　of　sight。　　The　coast…line　ran
almost　due　north　and　south；　while　the　volcanoes　that　dotted　it；
and　that　had　been　luminous　during　the　night；　now　revealed　their
nature　only　by　lines　of　smoke　and　vapours。　　They　were　struck　by
the　boldness　and　abruptness　of　the　scenery。　　The　mountains　and
cliffs　had　been　but　little　cut　down　by　water　and　frost　action；
and　seemed　in　the　full　vigour　of　their　youth；　which　was　what　the
travellers　had　a　right　to　expect　on　a　globe　that　was　still
cooling　and　shrinking；　and　consequently　throwing　up　ridges　in　the
shape　of　mountains　far　more　rapidly　than　a　planet　as　matured　and
quiescent　as　the　earth。　　The　absence　of　lakes　also　showed　them
that　there　had　been　no　Glacial　period；　in　the　latitudes　they　were
crossing；　for　a　very　long　time。
　　　
〃We　can　account　for　the　absence　of　ice…action　and　scratches；〃
said　Cortlandt；　〃in　one　of　two　ways。　　Either　the　proximity　of　the
internal　heat　to　the　surface　prevents　water　from　freezing　in　all
latitudes；　or　Jupiter's　axis　has　always　been　very　nearly
perpendicular　to　its　orbit；　and　consequently　the　thermometer　has
never　been　much　below　thirty…two　degrees　Fahrenheit；　for；　at　the
considerable　distance　we　are　now　from　the　sun；　it　is　easy　to
conceive　that；　with　the　axis　much　inclined；　there　might　be　cold
weather；　during　the　Northern　hemisphere's　winter；　that　would　last
for　about　six　of　our　years；　even　as　near　the　equator　as　this。　
The　substantiation　of　an　ice…cap　at　the　pole　will　disprove　the
first　hypothesis；　for　what　we　took　for　ice　before　alighting　may
have　been　but　banks　of　cloud；　since；　having　been　in　the　plane　of
the　planet's　equator　at　the　time；　we　had　naturally　but　a　very
oblique　view　of　the　poles；　while　the　absence　of　glacial　scratches
shows；　I　take　it；　that　though　the　axis　may　have　been　a　good　deal
more　inclined　than　at　present；　it　has　not；　at　all　events　since
Jupiter's　Palaeozoic　period；　been　as　much　so　as　that　of　Uranus　or
Venus。　　The　land　on　Jupiter；　corresponding　to　the　Laurentian
Hills　on　earth；　must　even　here　have　appeared　at　so　remote　a
period　that　the　first　surface　it　showed　must　long　since　have　been
worn　away；　and　therefore　any　impressions　it　received　have　also
been　erased。

〃Comparing　this　land　with　the　photographs　we　took　from　space；　I
should　say　it　is　the　eastern　of　the　two　crescent…shaped
continents　we　found　apparently　facing　each　other。　　Their　present
form　I　take　to　be　only　the　skeleton　outline　of　what　they　will　be
at　the　next　period　of　Jupiter's　development。　　They　will；　I
predict；　become　more　like　half　moons　than　crescents；　though　the
profile　may　be　much　indented　by　gulfs　and　bays；　their　superficial
area　being　greatly　increased；　and　the　intervening　ocean
correspondingly　narrowed。　　We　know　that　North　America　had　a　very
different　shape　during　the　Cretaceous　or　even　the　Middle　Tertiary
period　from　what　it　has　now；　and　that　the　Gulf　of　Mexico　extended
up　the　valley　of　the　Mississippi　as　far　as　the　Ohio；　by　the
presence　of　a　great　coral　reef　in　the　Ohio　River　near　Cincinnati。　
We　know　also　that　Florida　and　the　Southeastern　Atlantic　States
are　a　very　recent　addition　to　the　continent；　while　the　pampas　of
the　Argentine　Republic　have；　in　a　geological　sense；　but　just　been
upheaved　from　the　sea；　by　the　fact　that　the　rivers　are　all　on　the
surface；　not　having　had　time　to　cut　down　their　channels　below　the
surrounding　country。　　By　similar　reasoning；　we　know　that　the
canon　of　the　Colorado　is　a　very　old　region；　though　the
precipitateness　of　its　banks　is　due　to　the　absence　of　rain；　for　a
local　water…supply　would　cut　back　the　banks；　having　most　effect
where　they　were　steepest；　since　at　those　points　it　would　move
with　the　greatest　speed。　　Thus　the　majestic　canon　owes　its
existence　to　two　things：　the　length　of　time　the　river　has　been　at
work；　and　the　fact　that　the　water　flowing　through　it　comes　from
another　region　where；　of　course；　there　is　rain；　and　that　it　is
merely　in　transit；　and　so　affects　only　the　bed　on　which　it　moves。　
Granting　that　this　is　the　eastern　of　the　two　continents　we
observed；　it　evidently　corresponds　more　in　shape　to　the　Eastern
hemisphere　on　earth　than　to　the　New　World；　both　of　which　are　set
facing　one　another；　since　both　drain　towards　the　Atlantic　Ocean。　
But　the　analogy　here　holds　also；　for　the　past　outlines　of　the
Eastern　hemisphere　differed　radically　from　what　they　are　now。　
The　Mediterranean　Sea　was　formerly　of　far　greater　extent　than　we
see　it　to…day；　and　covered　nearly　the　whole　of　northern　Africa
and　the　old　upheaved　sea…bottom　that　we　see　in　the　Desert　of
Sahara。　　Much　of　this　great　desert；　as　we　know；　has　a
considerable　elevation；　though　part　of　it　is　still　below　the
level　of　the　Mediterranean。
　　　
〃Perhaps　a　more　striking　proof　of　this　than　are　the　remains　of
fishes　and　marine　life　that　are　found　there；　is　the　dearth　of
natural　harbours　and　indentations　in　Africa's　northern　coast；
while　just　opposite；　in　southern　Europe；　there　are　any　number；
which　shows　that　not　enough　time　has　elapsed　since　Africa's
upheaval　for　liquid　or　congealed　water　to　produce　them。　　Many　of
Europe's　best　harbours；　and　Boston's；　in　our　country；　have　been
dug　out　by　slow　ice…action　in　the　oft…recurring　Glacial　periods。　
The　Black　and　Caspian　Seas　were　larger　than　we　now　find　them；
while　the　Adriatic　extended　much　farther　into　the　continent；
covering　most　of　the　country　now　in　the　valley　of　the　Po。　　In
Europe　the　land　has；　of　course；　risen　also；　but　so　slowly　that
the　rivers　have　been　able　to　keep　their　channels　cut　down；　proof
of　their　ability　to　perform　which　feat　we　see　when　an　ancient
river　passes　through　a　ridge　of　hills　or　mountains。　　The　river
had　doubtless　been　there　long　before　the　mountains　began　to　rise；
but　their　elevation　was　so　gradual　that　the　rate　of　the　river's
cutting　down　equalled　or　exceeded　their　coming　up；　proof　of　which
we　have　in　the　patent　fact　that　the　ancient　river's　course
remains　unchanged；　and　is　at　right　angles　to　the　mountain　chain。　
From　all　of　which　we　see　that　the　Eastern　hemisphere's　crescent
hollowof　which；　I　take　it；　the　Mediterranean；　Black；　and
Caspian　Sea　depressions　are　the　remainshas　been　gradually
filled　in；　by　the　elevation　of　the　sea's　bottom；　and　the
extension　of　deltas　from　the　detrital　matter　brought　from　the
high　interior　of　the　continents　by　the　rivers；　or　by　the　combined
action　of　the　two。　　Now；　since　the　Gulf　of　Mexico　has　been
constantly　growing　smaller；　and　the　Mediterranean　is　being
invaded　by　the　land；　I　reason　that　similar　causes　will　produce
like　effects　here；　and　give　to　each　continent　an　area　far　greater
than　our　entire　globe。　　The　stormy　ocean　we　behold　in　the　west；
which　corresponds　to　our　Atlantic；　though　it　is　far　more　of　a
mare　clausum　in　the　geographical　sense；　is　also　destined　to
become　a　calm　and　placid　inland　sea。　　There　are；　of　course；
modifications　of　and　checks　to　the　laws　tending　to　increase　the
land　area。　　England　was　formerly　joined　to　the　continent；　the
land　connecting　the　two　having　been　rather　washed　away　by　the
waves　and　great　tides　than　by　any　sinking　of　the　English
Channel's　bottom；　the　whole　of　which　is　comparatively　shallow。　
Another　case　of　this　kind　is　seen　in　Cape　Cod　and　the　islands　of
Martha's　Vineyard　and　Nantucket；　all　of　which　are　washing　away　so
rapidly　that　they　would　probably　disappear　before　the　next
Glacial　period；　were　we　not　engaged　in　preventing　its　recurrence。　
These　detached　islands　and　sand…bars　once　formed　one　large
island；　which　at　a　still　earlier　time　undoubtedly　was　joined　to
the　mainland。　　The　sands　forming　the　detached　masses　are　in　a
great　processional　march　towards　the　equator；　but　it　is　the
result　simply　of　winds　and　waves；　there　being　no　indication　of
subside