Theintroductionofironasthematerialforshipbuildinghasimmenselyadvancedtheinterestsofsteamnavigation，asitenablesthebuilderstoconstructvesselsofgreatsizewiththefinestlines，soastoattainthehighestratesofspeed。
　　OnemighthavesupposedthatFrancisPettitSmithwouldderivesomesubstantialbenefitfromhisinvention，oratleastthattheShipPropellerCompanywoulddistributelargedividendsamongtheirproprietors。Nothingofthekind。Smithspenthismoney，hislabour，andhisingenuityinconferringagreatpublicbenefitwithoutreceivinganyadequatereward；andthecompany，insteadofdistributingdividends，lostabout50，000L。inintroducingthisgreatinvention；afterwhich，in1856，thepatent-rightexpired。Threehundredandtwenty-sevenshipsandvesselsofallclassesintheRoyalNavyhadthenbeenfittedwiththescrewpropeller，andamuchlargernumberinthemerchantservice；butsincethattimethenumberofscrewpropellersconstructedistobecountedbythousands。
　　Inhiscomparativelyimpoverishedconditionitwasfoundnecessarytodosomethingfortheinventor。TheCivilEngineers，withRobertStephenson，M。P。，inthechair，entertainedhimatadinnerandpresentedhimwithahandsomesalverandclaretjug。
　　Andthathemighthavesomethingtoputuponhissalverandintohisclaretjug，anumberofhisfriendsandadmirerssubscribedover2000L。asatestimonial。TheGovernmentappointedhimCuratorofthePatentMuseumatSouthKensington；theQueengrantedhimapensionontheCivilListfor200L。ayear；hewasraisedtothehonourofknighthoodinl87l，andthreeyearslaterhedied。
　　FrancisPettitSmithwasnotagreatinventor。Hehad，likemanyothers，inventedascrewpropeller。But，whilethoseothershadgivenuptheideaofprosecutingittoitscompletion，Smithstucktohisinventionwithdeterminedtenacity，andneverletitgountilhehadsecuredforitacompletetriumph。AsMr。
　　Stephensonobservedattheengineer’smeeting:“Mr。Smithhadworkedfromaplatformwhichmighthavebeenraisedbyothers，asWatthaddone，andasothergreatmenhaddone；buthehadmadeastrideinadvancewhichwasalmosttantamounttoanewinvention。
　　Itwasimpossibletooverratetheadvantageswhichthisandothercountrieshadderivedfromhisuntiringanddevotedpatienceinprosecutingtheinventiontoasuccessfulissue。“BaronCharlesDupincomparedthefarmerSmithwiththebarberArkwright:“Hehadthesameperseveranceandthesameindomitablecourage。
　　Thesetwomoralqualitiesenabledhimtotriumphovereveryobstacle。“Thiswasthemeritof“Screw“Smith——thathewasdeterminedtorealizewhathispredecessorshaddreamtofachieving；andheeventuallyaccomplishedhisgreatpurpose。
　　IntheTransactionsoftheInstitutionofNavalArchitectsfor1860，itwaspointedoutthatthegeneraldimensionsandformofbottomofthisshipwereverysimilartothemostfamousline-of-battleshipsbuiltdowntotheendoflastcentury，someofwhichweretheninexistence。AccordingtothecalculationofMr。Chatfield，ofHerMajesty’sdockyardatPlymouth，inapaperreadbeforetheBritishAssociationin1841onshipbuilding。
　　Thephrase“woodenwalls“isderivedfromtheGreek。WhenthecityofAthenswasonceindangerofbeingattackedanddestroyed，theoracleofDelphiwasconsulted。Theinhabitantsweretoldthattherewasnosafetyforthembutintheir“woodenwalls，“——thatistheirshipping。Astheyhadthenapowerfulfleet，theoraclegavethemrationaladvice，whichhadtheeffectofsavingtheAthenianpeople。
　　AnaccountoftheseisgivenbyBennetWoodcraftinhisSketchoftheOriginandProgressofSteamNavigation，London，1848。
　　SeeIndustrialBiography，pp。183-197，[6]ThestoryistoldinScribner’sMonthlyIllustratedMagazine，forApril1879。Ericsson’smodestbillwasonly$15，000fortwoyears’labour。Hewasputofffromyeartoyear，andatlengththeGovernmentrefusedtopaytheamount。“TheAmericanGovernment，“saystheeditorofScribner，“willnotappropriatethemoneytopayit，andthatisall。Itissaidtobethenatureofrepublicstobeungrateful；butmusttheyalsobedishonest？“
　　Nomanknowswhoinventedthemariner’scompass，orwhofirsthollowedoutacanoefromalog。Thepowertoobserveaccuratelythesun，moon，andplanets，soastofixavessel’sactualpositionwhenfaroutofsightofland，enablinglongvoyagestobesafelymade；themarvellousimprovementsinship-building，whichshortenedpassagesbysailingvessels，andvastlyreducedfreightsevenbeforesteamgaveanindependentforcetothecarrier——eachandallweredonebysmalladvances，whichtogethercontributedtothegeneralmovementofmankind……Eachowesalltotheothers。Theforgotteninventorsliveforeverintheusefulnessoftheworktheyhavedoneandtheprogresstheyhavestrivenfor。“——H。M。Hyndman。
　　OneofthemostextraordinarythingsconnectedwithAppliedScienceisthemethodbywhichtheNavigatorisenabledtofindtheexactspotofseaonwhichhisshiprides。Theremaybenothingbutwaterandskywithinhisview；hemaybeinthemidstoftheocean，orgraduallynearingtheland；thecurvatureoftheglobebafflesthesearchofhistelescope；butifhehaveacorrectchronometer，andcanmakeanastronomicalobservation，hemayreadilyascertainhislongitude，andknowhisapproximateposition——howfarheisfromhome，aswellasfromhisintendeddestination。Heisevenenabled，atsomespecialplace，tosenddownhisgrappling-ironsintothesea，andpickupanelectricalcableforexaminationandrepair。
　　ThisistheresultofaknowledgeofPracticalAstronomy。“Placeanastronomer，“saysMr。Newcomb，“onboardaship；blindfoldhim；carryhimbyanyroutetoanyoceanontheglobe，whetherunderthetropicsorinoneofthefrigidzones；landhimonthewildestrockthatcanbefound；removehisbandage，andgivehimachronometerregulatedtoGreenwichorWashingtontime，atransitinstrumentwiththeproperappliances，andthenecessarybooksandtables，andinasingleclearnighthecantellhispositionwithinahundredyardsbyobservationsofthestars。
　　This，fromautilitarianpointofview，isoneofthemostimportantoperationsofPracticalAstronomy。“[2]
　　TheMarineChronometerwastheoutcomeofthecryingwantofthesixteenthcenturyforaninstrumentthatshouldassistthenavigatortofindhislongitudeonthepathlessocean。Spainwasthentheprincipalnavalpower；shewasthemostpotentmonarchyinEurope，andheldhalfAmericaunderhersway。PhilipIII。
　　offered100，000crownsforanydiscoverybymeansofwhichthelongitudemightbedeterminedbyabettermethodthanbythelog，whichwasfoundverydefective。Hollandnextbecameagreatnavalpower，andfollowedtheexampleofSpaininoffering30，000
　　florinsforasimilardiscovery。Butthoughsomeeffortsweremade，nothingpracticalwasdone，principallythroughthedefectivestateofastronomicalinstruments。EnglandsucceededSpainandHollandasanavalpower；andwhenCharlesII。
　　establishedtheGreenwichObservatory，itwasmadeaspecialpointthatFlamsteed，theAstronomer-Royal，shoulddirecthisbestenergiestotheperfectingofamethodforfindingthelongitudebyastronomicalobservations。ButthoughFlamsteed，togetherwithHalleyandNewton，madesomeprogress，theywerepreventedfromobtainingultimatesuccessbythewantofefficientchronometersandthedefectivenatureofastronomicalinstruments。
　　NothingwasdoneuntilthereignofQueenAnne，whenapetitionwaspresentedtotheLegislatureonthe25thofMay，1714，by“severalcaptainsofHerMajesty’sships，merchantsinLondon，andcommandersofmerchantmen，inbehalfofthemselves，andofallothersconcernedinthenavigationofGreatBritain，“settingforththeimportanceoftheaccuratediscoveryofthelongitude，andtheinconvenienceanddangertowhichshipsweresubjectedfromthewantofsomesuitablemethodofdiscoveringit。Thepetitionwasreferredtoacommittee，whichtookevidenceonthesubject。ItappearsthatSirIsaacNewton，withhisextraordinarysagacity，hitthemarkinhisreport。“Oneis，“hesaid，“byawatchtokeeptimeexactly；but，byreasonofthemotionofaship，andthevariationofheatandcold，wetanddry，andthedifferenceofgravityindifferentlatitudes，suchawatchhathnotyetbeenmade。“
　　AnActwashoweverpassedintheSessionof1714，offeringaverylargepublicrewardtoinventors:10，000L。toanyonewhoshoulddiscoveramethodofdeterminingthelongitudetoonedegreeofagreatcircle，or60geographicalmiles；15，000L。ifitdeterminedthesametotwo-thirdsofthatdistance，or40geographicalmiles；and20，000L。ifitdeterminedthesametoone-halfofthesamedistance，or30geographicalmiles。CommissionerswereappointedbythesameAct，whowereinstructedthat“onemoietyorhalfpartofsuchrewardshallbedueandpaidwhenthesaidcommissioners，orthemajorpartofthem，doagreethatanysuchmethodextendstothesecurityofshipswithin80geographicalmilesoftheshore，whichareplacesofthegreatestdanger；andtheothermoietyorhalfpartwhenaship，bytheappointmentofthesaidcommissioners，orthemajorpartofthem，shallactuallysailovertheocean，fromGreatBritaintoanysuchportintheWestIndiesasthosecommissioners，orthemajorpartofthem，shallchooseornominatefortheexperiment，withoutlosingthelongitudebeyondthelimitsbeforementioned。“
　　Thetermsofthisofferindicatehowgreatmusthavebeentheriskandinconveniencewhichitwasdesiredtoremedy。Indeed，itisalmostinconceivablethatarewardsogreatcouldbeheldoutforamethodwhichwouldmerelyaffordsecuritywithineightygeographicalmiles！
　　Thissplendidrewardforamethodofdiscoveringthelongitudewasofferedtotheworld——toinventorsandscientificmenofallcountries——withoutrestrictionofrace，ornation，orlanguage。
　　Asmightnaturallybeexpected，theprospectofobtainingitstimulatedmanyingeniousmentomakesuggestionsandcontriveexperiments；butformanyyearsthesuccessfulconstructionofamarinetime-keeperseemedalmosthopeless。Atlength，tothesurpriseofeveryone，theprizewaswonbyavillagecarpenter——apersonofnoschool，oruniversity，orcollegewhatever。
　　EvensodistinguishedanartistandphilosopherasSirChristopherWrenwasengaged，aslateinhislifeastheyear1720，inattemptingtosolvethisimportantproblem。Ashasbeenobserved，inthememoirofhimcontainedinthe’BiographiaBritannica，’[3]“Thisnobleinvention，likesomeothersofthemostusefulonestohumanlife，seemstobereservedforthepeculiargloryofanordinarymechanic，who，byindefatigableindustry，undertheguidanceofnoordinarysagacity，hathseeminglyatlastsurmountedalldifficulties，andbroughtittoamostunexpecteddegreeofperfection。“Wherelearningandsciencefailed，naturalgeniusseemstohavetriumphed。
　　Thetruthis，thatthegreatmechanic，likethegreatpoet，isborn，notmade；andJohnHarrison，thewinnerofthefamousprize，wasabornmechanic。Hedidnot，however，accomplishhisobjectwithouttheexerciseofthegreatestskill，patience，andperseverance。Hiseffortswerelong，laborious，andsometimesapparentlyhopeless。Indeed，hislife，sofaraswecanascertainthefacts，affordsoneofthefinestexamplesofdifficultiesencounteredandtriumphantlyovercome，andofundauntedperseveranceeventuallycrownedbysuccess，whichistobefoundinthewholerangeofbiography。
　　NocompletenarrativeofHarrison’scareerwaseverwritten。
　　Onlyashortnoticeofhimappearsinthe’BiographiaBritannica，’publishedin1766，duringhislifetime’——thefactsofwhichwereobtainedfromhimself。Afewnoticesofhimappearinthe’AnnualRegister，’alsopublishedduringhislifetime。
　　Thefinalnoticeappearedinthevolumepublishedin1777，theyearafterhisdeath。NoLifeofhimhassinceappeared。Hadhebeenadestructivehero，andfoughtbattlesbylandorsea，weshouldhavehadbiographiesofhimwithoutend。Buthepursuedamorepeacefulandindustriouscourse。Hisdiscoveryconferredanincalculableadvantageonnavigation，andenabledinnumerablelivestobesavedatsea；italsoaddedtothedomainsofsciencebyitsmoreexactmeasurementoftime。Buthismemoryhasbeensufferedtopasssilentlyaway，withoutanyrecordbeingleftforthebenefitandadvantageofthosewhohavesucceededhim。ThefollowingmemoirincludesnearlyallthatisknownofthelifeandlaboursofJohnHarrison。