2016年12月英语四级阅读200篇：人工降雨思维导图

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　　Rainmaking 　　The idea of rainmaking is almost as old as man, but it was not until 1946 that man succeeded in making rain. In ancient times, rainmakers had claimed to bring rain

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2016年12月英语四级阅读200篇：人工降雨思维导图模板大纲

Rainmaking

Theideaofrainmakingisalmostasoldasman,butitwasnotuntil1946thatmansucceededinmakingrain.Inancienttimes,rainmakershadclaimedtobringrainbymanymethods:dancing,singing,killingvariouskindsoflivingcreatures(includinghumans),andblowingastreamofwaterintotheairfromakindofpipe.

Morerecently,somerainmakersclaimedtomakerainbyshootingguns,causingexplosions,orburningchemicals,thesmokeofwhichwassupposedtocauseraintofall.Theserainmakersaskedforasmuchas1,000dollarstomakeaninchofrain.Onewassoeffectivethathewasalmosthanged.Hewasbelievedtohavecausedatwenty-inchraininsouthernCaliforniathatfloodedtheland,killedseveralpeople,anddidmillionsofdollars'worthofdamage.

Before1946,rainmakerswereeitherliarsorhonestpeoplewhohappenedtohavegoodluck.ScientificrainmakingwasstartedinthatyearbyVincentJ.Schaefer,ascientistatthelaboratoriesoftheGeneralElectricCompanyinNewYorkState.Hissuccesswastheresultofaluckyaccidentthatchangedyearsoffailureintovictory.

Foralongtime,menhaveunderstoodwhereraincomesfrom.Waterfromthesurfaceofoceansandlakesbecomespartoftheair,whereitformscloudsfromwhichrainfalls.Butexactlywhatstartstheformationofraindropswasnotknownuntilquiterecently.AmannamedJohnAitkenprovedthatdropsofwatergatheraroundtinybitsofdustorothermatter.Thecentersofthedropsaresosmallthatthehumaneyecannotseethem.Withoutsuchcenters,itseems,raindropsdonotform.

DuringWorldWarII,Dr.IrvingLangmuir,ascientist,washiredbytheGeneralElectricCompanytostudyhowandwhyiceformsonthewingsofairplanes.HeandayoungassistantnamedSchaeferwenttoamountaininthestateofNewHampshire,wheresnowstormsarecommonandcoldwindsblow.

WhileinNewHampshire,LangmuirandSchaeferweresurprisedtolearnthatoftenthetemperatureofthecloudssurroundingthemwasfarbelowthefreezingpoint,andyeticedidnotformintheclouds.AftertheWar,Schaeferexperimentedwithamachinethatcreatedcold,moistairsimilartotheairfoundinclouds.Toimitatethemoistairofacloud,Schaeferwouldbreatheintothemachine.Thenhewoulddropintothefreezerabitofpowder,sugar,orsomeothersubstance.Forweeksandmonthshetriedeverythinghecouldimagine.Nothinghappened.Nocrystalsoficewereformed.Noneofthesubstanceswouldserveasthecenterofasnowcrystalorraindrop.

OneJulymorning,Schaeferwasdroppinginbitsofvarioussubstancesandwatchingtheunsuccessfulresults.Finally,afriendsuggestedthattheygotoeatlunch,andSchaefergladlywentwithhim.Asusual,heleftthecoverofthefreezerup,sincecoldairsinksandwouldnotescapefromthebox.

Returningfromlunch,Schaeferwasbeginningtoperformhisexperimentsagainwhenhehappenedtolookatthetemperatureofthefreezer.Ithadrisentoapointhigherthanthatrequiredforicecrystalstoremainsolid.Thewarmsummerweatherhadarrivedwithouthisnoticingit.Hewouldhavetobemorecarefulinthefuture.

Thereweretwochoicesnow.Hecouldclosethecoverandwaitforthefreezeritselftolowertheairtemperature,orhecouldmaketheprocessoccurfasterbyaddingdryice,agasinsolidformthatisvery,verycold.Hechosethelatterplan.Hedecidedtotryacontainerofdryice.

Ashedroppedthesteamingwhitedryiceintothefreezer,hehappenedtobreatheoutalargeamountofair.Andthere,beforehiseyes,ithappened!Hehadmadeicecrystals,notbyaddingcenterstothemoisturebutbycoolingthebreathsomuchthattheliquidhadtoformcrystals!Schaefercalledtohishelperstocomeandwatch.Thenhebegantoblowhisbreathintothefreezeranddroplargepiecesofdryicethroughittocreatecrystalswhichbecameatinysnowstormfallingslowlytothefloorofhislaboratory.

Ifhecouldmakesnowinafreezer,Schaeferthought,whycouldn'thedosoinarealcloud?Hedecidedtotryitinanairplanewithamachinetoblowdryiceoutintotheclouds.

OnacolddayinNovember,SchaeferandLangmuirsawcloudsinthesky,andSchaeferclimbedintotheairplane.Herealizedhewouldhavetoflysomedistancebeforefindingtherightkindofcloud—abiggrayonethatmustbefilledwithmoisture.Seeingone,Schaefertoldthepilotoftheplanetoflyabovethecloud.Atthepropertime,hestartedthemachine,anddryicebegantofallfromtheairplaneintothecloudbelow.Whenhalftheloadofdryicewasgone,themotorstoppedbecauseithadbecometoocold.Schaeferhadtothinkquickly.Hemerelythrewtheremainingdryiceoutofthewindowoftheplaneandintothecloudbelow.

Ontheground,Dr.Langmuirwatchedexcitedlyandsawsnowfallingfromthebottomofthecloud.WhenSchaeferreturnedtotheground,bluewithcold,Langmuirrantohim,shouting,"Youhavemadehistory!"Andindeedhehad.AlmostassoonasthenewsofhisaccomplishmentwassentacrosstheUnitedStatesandaroundtheworld,ahundredotherrainmakerswerethrowingdryiceintoclouds—or"seedingtheclouds"asitwascalled.

WhenSchaeferdiscoveredthaticecrystalscouldbeformedwithoutfindingtherightmaterialtomakecentersforthecrystals,hestoppedsearchingforsuchmaterials.ButanotheryoungworkeratGeneralElectric,BernardVonnegutbeganlookingthroughachemistrybookforsomechemicalcompoundthatmighthavetherightsizeandshapetoformcrystalsaroundit.Hefoundwhathewasbookingfor.Itwasacompoundcalledsilveriodide(碘化银).Hegotsomesilveriodideanddevelopedawayofburningittoproducetinyparticlesthatwouldseparateintheairandformsnow—hehoped.

Finallyheshotthematerialupintotheairandwaitedforthestorm.Nothinghappened.Hecouldn'tunderstandwhy.Thecompoundoughttoformentersforcrystals.Heaskedascientisttoexaminethechemicalshehadused.Therewasthetrouble.Thesilveriodidehehadusedwasnotpure.

Hegotmoreofthematerial,performedhisexperimentagain,andtherewerethesnowcrystals!Today,scientificrainmakersgenerallyusesilveriodide,Whichcanbesentintotheairfromthegroundbymeansofasimple,inexpensivemachine.Thisprocessismoresatisfactorythantheuseofdryicewhichcanbedestructive.

1.Humanbeingswereabletomakeraininancienttimes.

2.Dr.IrvingLangmuirandSchaeferwenttoNewHampshiretostudyhowandwhyiceformsonthewingsofairplanes.

3.Schaeferfoundouttheraindropscouldbemadewithouthavingtosearchtherightmaterialtomaketheircenters.

4.Usingsilveriodidetomakerainismoresatisfactorythanusingdryice.

5.Raincanbemadebyshootingsaltontotheclouds.

6.Schaeferfoundthewarmsummerweatherwasfavorableforrainmaking.