HarrisontothefavouroftheCommissionersappointedbyActofParliamentasapersonhighlydeservingofsuchfurtherencouragementandassistanceastheyshalljudgeproperandsufficienttofinishhisthirdmachine。“TheCommissionersgrantedhimafurthersumof500L。Harrisonwasalreadyreducedtonecessitouscircumstancesbyhiscontinuousapplicationtotheimprovementofthetimekeepers。Hehadalsogotintodebt，andrequiredfurtherassistancetoenablehimtoproceedwiththeirconstruction；buttheCommissionerswouldonlyhelphimbydriblets。
AlthoughHarrisonhadpromisedthatthethirdmachinewouldbereadyfortrialonAugust1，1743，itwasnotfinishedforsomeyearslater。InJune，1746，wefindhimagainappearingbeforetheBoard，askingforfurtherassistance。Whileproceedingwithhisworkhefounditnecessarytoaddanewspring，“havingspentmuchtimeandthoughtintemperingthem。“Another500L。wasvotedtoenablehimtopayhisdebts，tomaintainhimselfandfamily，andtocompletehischronometer。
ThreeyearslaterheexhibitedhisthirdmachinetotheRoyalSociety，andonthe30thofNovember，1749，hewasawardedtheGoldMedalfortheyear。Inpresentingit，Mr。Folkes，thePresident，saidtoMr。Harrison，“Idohere，bytheauthorityandinthenameoftheRoyalSocietyofLondonfortheimprovingofnaturalknowledge，presentyouwiththissmallbutfaithfultokenoftheirregardandesteem。Ido，intheirnamecongratulateyouuponthesuccessesyouhavealreadyhad，andImostsincerelywishthatallyourfuturetrialsmayineverywayproveanswerabletothesebeginnings，andthatthefullaccomplishmentofyourgreatundertakingmayatlastbecrownedwithallthereputationandadvantagetoyourselfthatyourwarmestwishesmaysuggest，andtowhichsomanyyearssolaudablyandsodiligentlyspentintheimprovementofthosetalentswhichGodAlmightyhasbestoweduponyou，willsojustlyentitleyourconstantandunweariedperseverance。“
Mr。Folkes，inhisspeech，spokeofMr。Harrisonas“oneofthemostmodestpersonshehadeverknown。Inspeaking，“hecontinued，“ofhisownperformances，hehasassuredmethat，fromtheimmensenumberofdiligentandaccurateexperimentshehasmade，andfromthesevereteststowhichhehasinmanywaysputhisinstrument，heexpectsheshallbeablewithsufficientcertainty，throughallthegreatestvarietyofseasonsandthemostirregularmotionsofthesea，tokeeptimeconstantly，withoutthevariationofsomuchasthreesecondsinaweek，——adegreeofexactnessthatisastonishingandevenstupendous，consideringtheimmensenumberofdifficulties，andthoseofverydifferentsorts，whichtheauthoroftheseinventionsmusthavehadtoencounterandstrugglewithal。“
Althoughitiscommonenoughnowtomakefirst-ratechronometers——sufficienttodeterminethelongitudewithalmostperfectaccuracyineveryclimeoftheworld——itwasverydifferentatthattime，whenHarrisonwasoccupiedwithhislaboriousexperiments。Althoughheconsideredhisthirdmachinetobetheneplusultraofscientificmechanism，heneverthelessproceededtoconstructafourthtimepiece，intheformofapocketwatchaboutfiveinchesindiameter。Hefoundtheprincipleswhichhehadadoptedinhislargermachinesappliedequallywellinthesmaller，andtheperformancesofthelastsurpassedhisutmostexpectations。Butinthemeantime，ashisthirdtimekeeperwas，inhisopinion，sufficienttosupplytherequirementsoftheBoardofLongitudeasrespectedthehighestrewardoffered，heappliedtotheCommissionersforleavetotrythatinstrumentonboardaroyalshiptosomeportintheWestIndies，asdirectedbythestatuteofQueenAnne。