a journey in other worlds-第7章

按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！


stones　bind　together　firmly；　and；　while　also　insoluble；　combine
considerable　bulk　with　weight。　　South　of　Hatteras；　where　stones
are　scarce；　the　sand　dredged　from　parts　of　the　channel　was　filled
into　the　crib；　the　surface　of　which　has　a　concave　metallic　cover；
a　trough　of　still　water　being　often　the　best　barrier　against　the
passage　of　waves。　　This　double　coast…line　has　been　a　great
benefit；　and　propelled　vessels　of　moderate　draught　can　range　in
smooth　water；　carrying　very　full　loads；　from　Labrador　to　the
Orinoco。　　The　exits　are；　of　course；　protected　by　a　line　of
cribbing　a　few　hundred　feet　to　seaward。
　　　
〃The　rocks　have　been　removed　from　all　channels　about　New　York　and
other　commercial　centres；　while　the　shallow　places　have　been
dredged　to　a　uniform　depth。　　This　diminishes　the　dangers　of
navigation　and　considerably　decreases　the　speed　with　which　the
tides　rush　through。　　Where　the　obstructions　consisted　of　reefs
surrounded　by　deep　water；　their　removal　with　explosives　was　easy；
the　shattered　fragments　being　allowed　to　sink　to　the　bottom　and
remain　there　beneath　the　danger　line。
　　　
〃Many　other　great　works　have　also　been　completed。　　The　canals　at
Nicaragua　have　been　in　operation　many　years；　it　having　been　found
best　to　have　several　sizes　of　locks；　and　to　use　the　large　ones
only　for　the　passage　of　large　vessels。　　The　improved　Erie　and
Champlain　Canals　also　enable　ships　four　hundred　feet　long　to
reach　New　York　from　the　Great　Lakes　via　the　Hudson　River。
　　　
〃For　flying；　we　have　an　aeroplane　that　came　in　when　we　devised　a
suitable　motor　power。　　This　is　obtained　from　very　light
paper…cell　batteries　that　combine　some　qualities　of　the　primary
and　secondary　type；　since　they　must　first　be　charged　from　a
dynamo；　after　which　they　can　supply　full　currents　for　one　hundred
hoursenough　to　take　them　around　the　globewhile　partly
consuming　the　elements　in　the　cells。　　The　power　is　applied
through　turbine　screws；　half　of　which　are　capable　of　propelling
the　flat　deck　in　its　inclined　position　at　sufficient　speed　to
prevent　its　falling。　　The　moving　parts　have　ball　bearings　and
friction　rollers；　lubrication　being　secured　automatically；　when
required；　by　a　supply　of　vaseline　that　melts　if　any　part　becomes
hot。　　All　the　framing　is　of　thin　but　very　durable　galvanized
aluminum；　which　has　superseded　steel　for　every　purpose　in　which
weight　is　not　an　advantage；　as　in　the　permanent　way　on　railways。　
The　air　ships；　whose　length　varies　from　fifty　to　five　hundred
feet；　have　rudders　for　giving　a　vertical　or　a　horizontal　motion；
and　several　strengthening　keels　that　prevent　leeway　when　turning。　
They　are　entirely　on　the　principle　of　birds；　maintaining
themselves　mechanically；　and　differing　thus　from　the　unwieldy
balloon。　　Starting　as　if　on　a　circular　railway；　against　the　wind；
they　rise　to　a　considerable　height；　and　then；　shutting　off　the
batteries；　coast　down　the　aerial　slope　at　a　rate　that　sometimes
touches　five　hundred　miles　an　hour。　　When　near　the　ground　the
helmsman　directs　the　prow　upward；　and；　again　turning　on　full
current；　rushes　up　the　slope　at　a　speed　that　far　exceeds　the
eagle's；　each　drop　of　two　miles　serving　to　take　the　machine
twenty　or　thirty；　though；　if　the　pilot　does　not　wish　to　soar；　or
if　there　is　a　fair　wind　at　a　given　height；　he　can　remain　in　that
stratum　of　the　atmosphere　by　moving　horizontally。　　He　can　also
maintain　his　elevation　when　moving　very　slowly；　and　though　the
headway　be　entirely　stopped；　the　descent　is　gradual　on　account　of
the　aeroplane's　great　spread；　the　batteries　and　motors　being
secured　to　the　under　side　of　the　deck。
　　　
〃The　motors　are　so　light　that　they　develop　two　horse　power　for
every　pound　of　their　weight；　while；　to　keep　the　frames　thin；　the
necessary　power　is　obtained　by　terrific　speed　of　the　moving
parts；　as　though　a　steam　engine；　to　avoid　great　pressure　in　its
cylinders；　had　a　long　stroke　and　ran　at　great　piston　speed；
which；　however；　is　no　disadvantage　to　the　rotary　motion　of　the
electric　motor；　there　being　no　reciprocating　cranks；　etc。；　that
must　be　started　and　stopped　at　each　revolution。
　　　
〃To　obviate　the　necessity　of　gearing　to　reduce　the　number　of
revolutions　to　those　possible　for　a　large　screw；　this　member　is
made　very　small；　and　allowed　to　revolve　three　thousand　times　a
minute；　so　that　the　requisite　power　is　obtained　with　great
simplicity　of　mechanism；　which　further　decreases　friction。　　The
shafts；　and　even　the　wires　connecting　the　batteries　with　the
motors；　are　made　large　and　hollow。　　Though　the　primary　battery
pure　and　simple；　as　the　result　of　great　recent　advances　in
chemistry；　seems　to　be　again　coming　up；　the　best　aeroplane
batteries　are　still　of　the　combination…　storage　type。　　These　have
been　so　perfected　that　eight　ounces　of　battery　yield　one　horse
power　for　six　hours；　so　that　two　pounds　of　battery　will　supply　a
horse　power　for　twenty…four　hours；　a　small　fifty…horse…power
aeroplane　being　therefore　able　to　fly　four　days　with　a　battery
weight　of　but　four　hundred　pounds。
　　　
〃Limestone　and　clarified　acid　are　the　principal　parts　of　these
batteries。　　It　was　known　long　ago　that　there　was　about　as　much
imprisoned　solar　energy　in　limestone　as　in　coal；　but　it　was　only
recently　that　we　discovered　this　way　of　releasing　and　using　it。
　　　
〃Common　salt　plays　an　important　part　in　many　of　our　chemical
reactions。　　By　combining　it　with　limestone；　and　treating　this
with　acid　jelly；　we　also　get　good　results　on　raising　to　the
boiling…point。
　　　
〃However　enjoyable　the　manly　sport　of　yachting　is　on　water；　how
vastly　more　interesting　and　fascinating　it　is　for　a　man　to　have　a
yacht　in　which　he　can　fly　to　Europe　in　one　day；　and　with　which
the　exploration　of　tropical　Africa　or　the　regions　about　the　poles
is　mere　child's　play；　while　giving　him　so　magnificent　a
bird's…eye　view！　　Many　seemingly　insoluble　problems　are　solved　by
the　advent　of　these　birds。　　Having　as　their　halo　the　enforcement
of　peace；　they　have　in　truth　taken　us　a　long　step　towards　heaven；
and　to　the　co…operation　and　higher　civilization　that　followed　we
shall　owe　much　of　the　success　of　the　great　experiment　on　Mother
Earth　now　about　to　be　tried。
　　　
〃Another　change　that　came　in　with　a　rush　upon　the　discovery　of　a
battery　with　insignificant　weight；　compact　form；　and　great
capacity；　was　the　substitution　of　electricity　for　animal　power
for　the　movement　of　all　vehicles。　　This；　of　necessity　brought　in
good　roads；　the　results　obtainable　on　such　being　so　much　greater
than　on　bad　ones　that　a　universal　demand　for　them　arose。　　This
was　in　a　sense　cumulative；　since　the　better　the　streets　and　roads
became；　the　greater　the　inducement　to　have　an　electric　carriage。　
The　work　of　opening　up　the　country　far　and　near；　by　straightening
and　improving　existing　roads；　and　laying　out　new　ones　that
combine　the　solidity　of　the　Appian　Way　with　the　smoothness　of
modern　asphalt；　was　largely　done　by　convicts；　working　under　the
direction　of　State　and　Government　engineers。　　Every　State
contained　a　horde　of　these　unprofitable　boarders；　who；　as　they
formerly　worked；　interfered　with　honest　labour；　and　when　idle　got
into　trouble。　　City　streets　had　been　paved　by　the　municipality；
country　roads　attended　to　by　the　farmers；　usually　very
unscientifically。　　Here　was　a　field　in　which　convict　labour　would
not　compete；　and　an　important　work　could　be　done。　　When　once　this
was　made　the　law；　every　year　showed　improvement；　while　the
convicts　had　useful　and　healthful　occupation。
　　　
〃The　electric　phaetons；　as　those　for　high　speed　are　called；　have
three　and　four　wheels；　and　weigh；　including　battery　and　motor；
five　hundred　to　four　thousand　pounds。　　With　hollow　but　immensely
strong　galvanically　treated　aluminum　frames　and　pneumatic　or
cushion　tires；　they　run　at　thirty…five　and　forty　miles　an　hour　on
country　roads；　and　attain　a　speed　over　forty　on　city　streets；　and
can　maintain　this　rate　without　recharging　for　several　days。　　They
can　therefore　roam　over　the　roads　of　the　entire　hemisphere；　from
the　fertile　valley　of　the　Peace　and　grey　shores　of　Hudson　Bay；　to
beautiful　Lake　Nicaragua；　the　River　Plate；　and　Patagonia；
improving　man　by　bringing　him　close　to　Nature；　while　they　combine
the　sensations　of　coasting　with　the　interest　of　seeing　the
country　well。
　　　
〃To　recharge　the　batteries；　which　can　be　done　in　almost　every
town　and　village；　two　copper　pins　attached　to　insulated　copper
wires　are　shoved　into　smooth…bored　holes。　　These　drop　out　of
themselves　by　fusing　a　small　lead　ribbon；　owing　to　the　increased
resistance；　when　the　acid　in　the　batteries　begins　to　'boil；'
though　there　is；　of　course；　but　little　heat　in　this；　the　function
of　charging　being　merely　to　bring　about　the　condition　in　which
part　of　the　limestone　can　be　consumed；　the　batteries　themselves；
when　in　constant　use；　requiring　to　be　renewed　about　once　a　month。　
A　handle　at　the　box　seat　turns　on　any　part　of　the　attainable
current；　for　either　going　ahead　or　reversing；　there　being　six　or
eight　degrees　of　speed　for　both　directions；　while　the　steering　is
done　with　a　small　wheel。
　　　
〃Light　but　powerful　batteries　and　motors　have　also　been　fitted　on
bicycles；　which　can　act　either　as　auxiliaries　for　hill…climbing
or　in　case　of　head　wind；　or　they　can　propel　the　machine
altogether。
　　　
〃Gradually　the　width　of　the　streets　became　insufficient　for　the
traffic；　although　the　elimination　of　horses　and　the　consequent
increase　in　speed　greatly　augmented　their　carrying　capacity；
until　recently　a　new　system　came　in。　　The　whole　width　of　the
avenues　and　streets　in　the　business　parts　of　the　city；　including
the　former　sidewalks；　is　given　up　to　wheel　traffic；　an　iron　ridge
extending　along　the　exact　centre　to　compel　vehicles　to　keep　to
the　right。　　Strips　of　nickel　painted　white；　and　showing　a　bright
phosphorescence　at　night；　are　let　into　the　metal　pavement　flush
with　the　surface；　and　run　parallel　to　this　ridge　at　distances　of
ten　to　fifteen　feet；　dividing　each　half　of　the　avenue　into　four
or　five　sections；　their　width　increasing　as　they　approach　the
middle。　　All　trucks　or　drays　moving　at　less　than　seven　miles　an
hour　are　obliged　to　keep　in　the　section　nearest　the　building
line；　those　running　between　seven　and　fifteen　in　the　next；
fifteen　to　twenty…five　in　the　third；　twenty…five　to　thirty…five
in　the　fourth；　and　everything　faster　than　that　in　the　section
next　the　ridge；　unless　the　avenue　or　street　is　wide　enough　for
further　subdivisions。　　If　it　is　wide　enough　for　only　four　or
less；　the　fastest　vehicles　must　keep　next　the　middle；　and　limit
their　speed　to　the　rate　allowed　in　that　section；　which　is　marked
at　every　crossing　in　white　letters　sufficiently　large　for　him
that　runs　to　read。　　It　is　therefore　only　in　the　wide
thoroughfares　that　very　high　speed　can　be　attained。　　In　addition
to　the　crank　that　corresponds　to　a　throttle；　there　is　a　gauge　on
every　vehicle；　which　shows　its　exact　speed　in　miles　per　hour；　by
gearing　operated　by　the　revolutions　of　the　wheels。
　　　
〃The　policemen　on　duty　also　have　instantaneous　kodaks　mounted　on
tripods；　which　show　the　position　of　any　carriage　at　half…　and
quarter…second　intervals；　by　which　it　is　easy　to　ascertain　the
exact　speed；　should　the　officers　be　unable　to　judge　it　by　the
eye；　so　there　i