a journey in other worlds-第6部分

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use；　so　that　only　the　frames　are　visible。　　Sometimes　these　also
fold　and　are　housed；　or　wholly　disappear　within　the　mast。　
Steam…boilers　are　also　placed　at　the　foci　of　huge　concave
mirrors；　often　a　hundred　feet　in　diameter；　the　required　heat
being　supplied　by　the　sun；　without　smoke；　instead　of　by　bulky　and
dirty　coal。　　This　discovery　gave　commercial　value　to　Sahara　and
other　tropical　deserts；　which　are　now　desirable　for　mill…sites
and　for　generating　power；　on　account　of　the　directness　with　which
they　receive　the　sun's　rays　and　their　freedom　from　clouds。　　Mile
after　mile　Africa　has　been　won　for　the　uses　of　civilization；　till
great　stretches　that　were　considered　impassible　are　as　productive
as　gardens。　　Our　condensers；　which　compress；　cool；　and　rarefy
air；　enabling　travellers　to　obtain　water　and　even　ice　from　the
atmosphere；　are　great　aids　in　desert　exploration；　removing
absolutely　the　principal　distress　of　the　ancient　caravan。　　The
erstwhile　'Dark　Continent'　has　a　larger　white　population　now　than
North　America　had　a　hundred　years　ago；　and　has　this　advantage　for
the　future；　that　it　contains　11；600；000　square　miles；　while　North
America　has　less　than　9；000；000。　　Every　part　of　the　globe　will
soon　sustain　about　as　large　and　prosperous　a　population　as　the
amount　of　energy　it　receives　from　the　sun　and　other　sources　will
warrant；　public　debts　and　the　efficiency　of　the　governments　being
the　variable　elements。
　　　
〃The　rabbits　in　Australia；　and　the　far　more　objectionable
poisonous　snakes　in　South　America　and　India；　have　been
exterminated　by　the　capture　of　a　few　dozen　of　the　creatures　in
the　infested　districts；　their　inoculation　with　the　virus　similar
to　the　murus　tiphi；　tuberculosis　or　any　other　contagious…germ
complaint　to　which　the　species　treated　was　particularly
susceptible；　and　the　release　of　these　individuals　when　the
disease　was　seen　to　be　taking　hold。　　The　rabbits　and　serpents
released　at　once　returned　to　their　old　haunts；　carrying　the
plague　far　and　wide。　　The　unfortunate　rabbits　were　greatly
commiserated　even　by　the　medicos　that　wielded　the　death…dealing
syringe；　but；　fortunately　for　themselves；　they　died　easily。　　The
reptiles；　perhaps　on　account　of　the　wider　distribution　of　the
nerve　centres；　had　more　lingering　but　not　painful　deaths；　often；
while　in　articulo　mortis；　leaving　the　holes　with　which　they
seemed　to　connect　their　discomfort；　and　making　a　final　struggle
along　the　ground；　only　to　die　more　quickly　as　a　result　of　their
exertions。　　We　have　applied　this　also　to　the　potato…bug；　locust；
and　other　insect　pests；　no　victim　being　too　small　for　the
ubiquitous；　subtle　germ；　which；　properly　cultivated　and　utilized；
has　become　one　of　man's　best　friends。
　　　
〃We　have　microbe　tests　that　show　us　as　unmistakably　whether　the
germs　of　any　particular　diseaselike　malaria；　typhoid；　or
scarlet　feverare　present　in　the　air；　as　litmus…paper　shows
alkalinity　of　a　solution。　　We　also　inoculate　as　a　preventive
against　these　and　almost　all　other　germ　diseases；　with　the　same
success　that　we　vaccinate　for　smallpox。
　　　
〃The　medicinal　properties　of　all　articles　of　food　are　so　well
understood　also；　that　most　cures　are　brought　about　simply　by
dieting。　　This；　reminds　me　of　the　mistakes　perpetrated　on　a
friend　of　mine　who　called　in　Dr。　Grave…Powders；　one　of　the
old…school　physicians；　to　be　treated　for　insomnia　and　dyspepsia。　
This　old　numskull　restricted　his　diet；　gave　him　huge　doses　of
medicine；　and　decided　most　learnedly　that　he　was　daily　growing
worse。　　Concluding　that　he　had　but　a　short　time　to　live；　my
friend　threw　away　the　nauseating　medicines；　ate　whatever　he　had　a
natural　desire　for；　and　was　soon　as　well　as　everthe　obvious
moral　of　which　is；　that　we　can　get　whatever　treatment　we　need
most　beneficially　from　our　food。　　Our　physicians　are　most　serious
and　thoughtful　men。　　They　never　claim　to　be　infallible；　but　study
scientifically　to　increase　their　knowledge　and　improve　the
methods　of　treatment。　　As　a　result　of　this；　fresh　air；　regular
exercise　for　both　sexes；　with　better　conditions；　and　the
preservation　of　the　lives　of　children　that　formerly　died　by
thousands　from　preventable　causes；　the　physique；　especially　of
women；　is　wonderfully　improved；　and　the　average　longevity　is
already　over　sixty。
　　　
〃Our　social　structure；　to　be　brief；　is　based　on　science；　or　the
conservation　of　energy；　as　the　Greek　philosophers　predicted。　　It
was　known　to　them　that　a　certain　amount　of　power　would　produce
only　a　certain　amount　of　workthat　is；　the　weight　of　a　clock　in
descending　or　a　spring　in　uncoiling　returns　theoretically　the
amount　of　work　expended　in　raising　or　coiling　it；　and　in　no
possible　way　can　it　do　more。　　In　practice；　on　account　of
friction；　etc。；　we　know　it　does　less。　　This　law；　being
invariable；　of　course　limits　us；　as　it　did　Archimedes　and
Pythagoras；　we　have　simply　utilized　sources　of　power　that　their
clumsy　workmen　allowed　to　escape。　　Of　the　four　principal
sourcesfood；　fuel；　wind；　and　tideincluding　harnessed
waterfalls；　the　last　two　do　by　far　the　most　work。　　Much　of　the
electrical　energy　in　every　thunderstorm　is　also　captured　and
condensed　in　our　capacious　storage　batteries；　as　natural　hygeia
in　the　form　of　rain　was　and　is　still　caught　in　our　country
cisterns。　　Every　exposed　place　is　crowned　by　a　cluster　of　huge
windmills　that　lift　water　to　some　pond　or　reservoir　placed　as
high　as　possible。　　Every　stiff　breeze；　therefore；　raises　millions
of　tons　of　water　which　　operate　hydraulic　turbines　as　required。　
Incidentally　these　storage　reservoirs；　by　increasing　the　surface
exposed　to　evaporation　and　the　consequent　rainfall；　have　a　very
beneficial　effect　on　the　dry　regions　in　the　interior　of　the
continent；　and　in　some　cases　have　almost　superseded　irrigation。　
The　windmill　and　dynamo　thus　utilize　bleak　mountain…tops　that；
till　their　discovery；　seemed　to　be　but　indifferent　successes　in
Dame　Nature's　domain。　　The　electricity　generated　by　these；　in
connection　with　that　obtained　by　waterfalls；　tidal　dynamos；
thunderstorms；　chemical　action；　and　slow…moving
quadruple…expansion　steam　engines；　provides　the　power　required　to
run　our　electric　ships　and　water…spiders；　railways；　and
stationary　and　portable　motors；　for　heating　the　cables　laid　along
the　bottom　of　our　canals　to　prevent　their　freezing　in　winter；　and
for　almost　every　conceivable　purpose。　　Sometimes　a　man　has　a
windmill　on　his　roof　for　light　and　heat；　then；　the　harder　the
wintry　blasts　may　blow　the　brighter　and　warmer　becomes　the　house；
the　current　passing　through　a　storage　battery　to　make　it　more
steady。　　The　operation　of　our　ordinary　electric　railways　is　very
simple：　the　current　is　taken　from　an　overhead；　side；　or
underneath　wire；　directly　through　the　air；　without　the
intervention　of　a　trolley；　and　the　fast　cars；　for　they　are　no
longer　run　in　trains；　make　five　miles　a　minute。　　The　entire
weight　of　each　car　being　used　for　its　own　traction；　it　can　ascend
very　steep　grades；　and　can　attain　high　speed　or　stop　very
quickly。
　　　
〃Another　form　is　the　magnetic　railway；　on　which　the　cars　are
wedge…shaped　at　both　ends；　and　moved　by　huge　magnets　weighing
four　thousand　tons　each；　placed　fifty　miles　apart。　　On　passing　a
magnet；　the　nature　of　the　electricity　charging　a　car　is
automatically　changed　from　positive　to　negative；　or　vice　versa；
to　that　of　the　magnet　just　passed；　so　that　it　repels　while　the
next　attracts。　　The　successive　magnets　are　charged　oppositely；
the　sections　being　divided　halfway　between　by　insulators；　the
nature　of　the　electricity　in　each　section　being　governed　by　the
charge　in　the　magnet。　　To　prevent　one　kind　of　electricity　from
uniting　with　and　neutralizing　that　in　the　next　section　by　passing
through　the　car　at　the　moment　of　transit；　there　is　a　〃dead
stretch〃　of　fifty　yards　with　rails　not　charged　at　all　between　the
sections。　　This　change　in　the　nature　of　the　electricity　is
repeated　automatically　every　fifty　miles；　and　obviates　the
necessity　of　revolving　machinery；　the　rails　aiding　communication。

〃Magnetism　being　practically　as　instantaneous　as　gravitation；　the
only　limitations　to　speed　are　the　electrical　pressure　at　the
magnets；　the　resistance　of　the　air；　and　the　danger　of　the　wheels
bursting　from　centrifugal　force。　　The　first　can　seemingly　be
increased　without　limit；　the　atmospheric　resistance　is　about　to
be　reduced　by　running　the　cars　hermetically　sealed　through　a
partial　vacuum　in　a　steel　and　toughened　glass　tube；　while　the
third　has　been　removed　indefinitely　by　the　use　of　galvanized
aluminum；　which　bears　about　the　same　relation　to　ordinary
aluminum　that　steel　does　to　iron；　and　which　has　twice　the　tensile
strength　and　but　one　third　the　weight　of　steel。　　In　some　cases
the　rails　are　made　turned　in；　so　that　it　would　be　impossible　for
a　car　to　leave　the　track　without　the　road…bed's　being　totally
demolished；　but　in　most　cases　this　is　found　to　be　unnecessary；
for　no　through　line　has　a　curve　on　its　vast　stretches　with　a
radius　of　less　than　half　a　mile。　　Rails；　one　hundred　and　sixty
pounds　to　the　yard；　are　set　in　grooved　steel　ties；　which　in　turn
are　held　by　a　concrete　road…bed　consisting　of　broken　stone　and
cement；　making　spreading　rails　and　loose　ballast　impossible。　　A
large　increase　in　capital　was　necessary　for　these　improvements；
the　elimination　of　curves　being　the　most　laborious　part；
requiring　bridges；　cuttings；　and　embankments　that　dwarf　the
Pyramids　and　would　have　made　the　ancient　Pharaohs　open　their
eyes；　but　with　the　low　rate　of　interest　on　bonds；　the　slight　cost
of　power；　and　great　increase　in　business；　the　venture　was　a
success；　and　we　are　now　in　sight　of　further　advances　that　will
enable　a　traveller　in　a　high　latitude　moving　west　to　keep　pace
with　the　sun；　and；　should　he　wish　it；　to　have　unending　day。〃



　　　　　　　　　　　　　　　　　　　　　　　　　　　CHAPTER　V。

　　　　　　　　　　　　　　　DR。　CORTLANDT'S　HISTORY　CONTINUED。
　　
〃In　marine　transportation　we　have　two　methods；　one　for　freight
and　another　for　passengers。　　The　old…fashioned　deeply　immersed
ship　has　not　changed　radically　from　the　steam　and　sailing　vessels
of　the　last　century；　except　that　electricity　has　superseded　all
other　motive　powers。　　Steamers　gradually　passed　through　the　five
hundred…；　six　hundred…；　and　seven