TheGreateInventionofAlgebra Doeyounotherestartle,toseeeverydaysomeofyourinventionstakenfromyou; forIrememberlongsinceyoutoldmeasmuch(asKeplerhasjustpublished)that themotionsoftheplanetswerenotperfectcircles. Soyoutaughtmethecurious waytoobserveweightinWater,andwithinawhileafterGhetaldicomesoutwithit inprint.AlittlebeforeVietapreventedyouoftheGharlandforthegreateInvention ofAlgebra.AlthesewereyourdeuesandmanieothersthatIcouldmention;andyet toogreatreservednessehathrob’dyouoftheseglories...Onlieletthisremember you,thatitispossiblebytomuchprocrastinationtobepreventedinthehonorof someofyourrarestinventionsandspeculations. WilliamLowertoThomasHarriot,6February1610 The Greate Invention of Algebra T H O M A S H A R R I O T’S T R E A T I S E O N E Q U A T I O N S Jacqueline A. Stedall CliffordNortonStudentintheHistoryofScience, TheQueen’sCollege,Oxford, and OpenUniversity GreatClarendonStreet,OxfordOX26DP OxfordUniversityPressisadepartmentoftheUniversityofOxford. ItfurtherstheUniversity’sobjectiveofexcellenceinresearch,scholarship, andeducationbypublishingworldwidein Oxford NewYork Auckland Bangkok BuenosAires CapeTown Chennai DaresSalaam Delhi HongKong Istanbul Karachi Kolkata KualaLumpur Madrid Melbourne MexicoCity Mumbai Nairobi SãoPaulo Shanghai Taipei Tokyo Toronto OxfordisaregisteredtrademarkofOxfordUniversityPress intheUKandincertainothercountries PublishedintheUnitedStates byOxfordUniversityPressInc.,NewYork ©OxfordUniversityPress,2003 Themoralrightsoftheauthorhavebeenasserted DatabaserightOxfordUniversityPress(maker) Firstpublished2003 Allrightsreserved.Nopartofthispublicationmaybereproduced, storedinaretrievalsystem,ortransmitted,inanyformorbyanymeans, withoutthepriorpermissioninwritingofOxfordUniversityPress, orasexpresslypermittedbylaw,orundertermsagreedwiththeappropriate reprographicsrightsorganization.Enquiriesconcerningreproduction outsidethescopeoftheaboveshouldbesenttotheRightsDepartment, OxfordUniversityPress,attheaddressabove Youmustnotcirculatethisbookinanyotherbindingorcover andyoumustimposethissameconditiononanyacquirer AcataloguerecordforthistitleisavailablefromtheBritishLibrary LibraryofCongressCataloginginPublicationData Stedall,Jacqueline. Thegreateinventionofalgebra:ThomasHarriot’streatiseonequations/JacquelineA.Stedall. Includesbibliographicalreferencesandindex. 1.Equations 2.Algebra–England–History–17thcentury 3.Harriot,Thomas, 1560-1621–Influence I.Harriot,Thomas,1560-1621 II.Title. QA211.S772003 512.9’4–dc21 2002042558 ISBN 0 19 852602 4(acid-freepaper) 10 9 8 7 6 5 4 3 2 1 TypesetbyCephaImagingPvt.Ltd. PrintedinGreatBritain onacid-freepaperbyBiddlesLtd,Guildford&King’sLynn Dedication ForRobertFox,JohnNorth andPeterNeumann This page intentionally left blank Acknowledgements I amindebtedtoanumberoflibrariansandarchivistswhohavehelped me to locate and use the manuscripts of which this edition is based, firstandforemosttoColinHarrisandhisstaffattheBodleianLibrary, Oxford, whohavesooftenandsoreadilyprovidedmewiththehefty boxescontainingthephotocopiesoftheHarriotandCavendishpapers.Iam also grateful to Alison McCann of the West Sussex Record Office for her assistancewiththePetworthpapersandtoLordEgremontforhispermission to copy and use them. Sarah Wickham of Lambeth Palace Library helped with great efficiency with the Torporley manuscripts, and the archivists of theNorthamptonshireRecordOfficewiththeIshampapers. I would like to give special thanks also to Muriel Seltman who first introducedmetoHarriot’smanuscripts,andwhohasgivenmemuchwarm support, and to Stephen Clucas who helped me in researching details of Harriot’slifeandacquaintances. While preparing this edition I have held the Clifford Norton Studentship in the History of Science at The Queen’s College, Oxford, and have been a member of the Centre for the History of the Mathematical Sciences at the Open University. I have dedicated this book to three people who have takenaparticularinterestinthisprojectandwhohavegivenmeunstinting encouragementandsupport. TheQueen’sCollege,Oxford J.A.S. April2002 vii This page intentionally left blank Contents Illustrations xi INTRODUCTION I. TheTreatiseonequations 3 Harriot,TorporleyandViète 3 Harriot’snotation 7 TheOperationsofarithmeticinletters 8 TheTreatiseonequations 11 II. Harriot’salgebraafter1621 17 ThePraxis 20 TheCorrector 22 TheSummary 24 III. Harriot’sreputationandinfluence 26 TREATISEONEQUATIONS Operationsofarithmeticinletters 39 Treatiseonequations Section(a):Onsolvingequationsinnumbers 45 Section(b):Onsolvingequationsinnumbers 65 Section(c):Onsolvingequationsinnumbers 87 Section(d):Onthegenerationofcanonicalequations 125 Section(e):Onsolvingequationsbyreduction 175 Section(f):Onsolvingequationsbyreduction 239 ix