ThefirstpartofthisvolumeisbasedonacoursetaughtatPrinceton Universityin1961-62;atthattime,anexcellentsetofnoteswasprepared byDavidCantor,anditwasoriginallymyintentiontomakethesenotes availabletothemathematicalpublicwithonlyquiteminorchanges.Then,amongsomeoldpapersofmine,Iaccidentallycameacrossalong-forgottenmanuscriptbyChevalley,ofpre-warvintage(forgotten,thatistosay,bothbymeandbyitsauthor)which,tomytasteatleast,seemedtohaveagedverywell.Itcontainedabriefbutessentiallycom-pleteaccountofthemainfeaturesofclassfieldtheory,bothlocalandglobal;anditsoonbecameobviousthattheusefulnessoftheintendedvolumewouldbegreatlyenhancedifIincludedsuchatreatmentofthistopic.Ithadtobeexpanded,inaccordancewithmyownplans,butitsoutlinecouldbepreservedwithoutmuchchange.Infact,Ihaveadheredtoitrathercloselyatsomecriticalpoints.