教材文本 unit 2 reading

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1、Unit2SailingtheOceansPre-readingLookatthepictures.Thenanswerthequestions.1Howdoyouthinkseamenfoundtheirwaybeforemodernaccuratemethodsofnavigationwereinvented?2Whichdoyouthinkwaseasiertoworkout:latitudeorlongitude?3Canyouidentifytheseearlynavigationalinstrumentsseamenusedandexplainhowtheyareused

2、?1______________2______________3______________4______________4Whichonesdoyouthinkarestillusedtoday?Nowreadaboutwhatnavigationwaslikebeforemoderninstrumentswereused.ReadingSAILINGTHEOCEANSWemaywellwonderhowseamenexploredtheoceansbeforelatitudeandlongitudemadeitpossibletoplotaship’spositiononamap

3、.Thevoyagesoftravellersbeforethe17thcenturyshowthattheywerenotatthemercyoftheseaeventhoughtheydidnothavemodernnavigationalaids.Sohowdidtheynavigatesowell?Readthesepagesfromanencyclopedia.Pagel:UsingnaturetohelpKeepingalongsidethecoastlineThisseemstohavebeenthefirstandmostusefulformofexploration

4、whichcarriedtheminimumamountofrisk.Usingcelestialbodies●NorthStarAttheNorthPoletheNorthStarisatitshighestpositioninthesky,butattheequatoritisalongthehorizon.Soaccomplishednavigatorswereabletouseittoplottheirpositions.●SunOnacleardayespeciallyduringthesummerthesailorscouldusethesunoverheadatmidd

5、aytonavigateby.Theycanusetheheightofthesuntoworkouttheirlatitude.●CloudsSeacaptainsobservedthecloudsoverislands.Thereisaspecialcloudformationwhichindicatesthereislandcloseby.Usingwildlife●SeaweedSailorsoftensawseaweedintheseaandcouldtellbythecolourandsmellhowlongithadbeenthere.Ifitwasfreshandsm

6、elledstrongly,thentheshipwasclosetoland.●BirdsSeabirdscouldbeusedtoshowthewaytolandwhenitwasnowheretobeseen.Intheeveningnestingbirdsreturntolandandtheirnests.Soseamencouldfollowthebirdstolandeveniftheywereoffshoreandintheopensea.Usingtheweather●FogFoggathersatseaaswellasoverstreamsorrivers.Seam

7、enusedittohelpidentifythepositionofastreamorriverwhentheywereclosetoland.●WindsWiseseamenusedthewindstodirecttheirsailing.Theycouldacceleratethespeed,buttheycouldalsobedangerous.SotheVikingswouldobservethewindsbeforeandduringtheir