Meanwhile，astronomersacrossthechannelwerebynomeansidle。InFranceseveralsuccessfulobserversweremakingmanyadditionstothealreadylonglistofobservationsofthefirstastronomeroftheRoyalObservatoryofParis，DominicCassini1625-1712，whosereputationamonghiscontemporarieswasmuchgreaterthanamongsucceedinggenerationsofastronomers。PerhapsthemostdeservingofthesesuccessorswasNicolasLouisdeLacaille1713-1762，atheologianwhohadbeeneducatedattheexpenseoftheDukeofBourbon，andwho，soonaftercompletinghisclericalstudies，cameunderthepatronageofCassini，whoseattentionhadbeencalledtotheyoungman’sinterestinthesciences。OneofLacaille’sfirstunder-takingswastheremeasuringoftheFrenchareofthemeridian，whichhadbeenincorrectlymeasuredbyhispatronin1684。Thiswasbegunin1739，andoccupiedhimfortwoyearsbeforesuccessfullycompleted。Asareward，however，hewasadmittedtotheacademyandappointedmathematicalprofessorinMazarinCollege。
In1751hewenttotheCapeofGoodHopeforthepurposeofdeterminingthesun’sparallaxbyobservationsoftheparallaxesofMarsandVenus，andincidentallytomakeobservationsontheothersouthernhemispherestars。Theresultsofthisundertakingweremostsuccessful，andweregiveninhisCoelumaustralestelligerum，etc。，publishedin1763。Inthisheshowsthatinthecourseofasingleyearhehadobservedsometenthousandstars，andcomputedtheplacesofonethousandninehundredandforty-twoofthem，measuredadegreeofthemeridian，andmademanyobservationsofthemoon——productiveindustryseldomequalledinasingleyearinanyfield。Theseobservationswereofgreatservicetotheastronomers，astheyaffordedtheopportunityofcomparingthestarsofthesouthernhemispherewiththoseofthenorthern，whichwerebeingobservedsimultaneouslybyLelandeatBerlin。
Lacaille’sobservationsfollowedcloselyuponthedeterminationofanabsorbingquestionwhichoccupiedtheattentionoftheastronomersintheearlypartofthecentury。Thisquestionwasastotheshapeoftheearth——whetheritwasactuallyflattenedatthepoles。TosettlethisquestiononceforalltheAcademyofSciencesdecidedtomaketheactualmeasurementofthelengthoftwodegrees，oneasnearthepoleaspossible，theotherattheequator。
Accordingly，threeastronomers，Godin，Bouguer，andLaCondamine，madethejourneytoaspotontheequatorinPeru，whilefourastronomers，Camus，Clairaut，Maupertuis，andLemonnier，madeavoyagetoaplaceselectedinLapland。Theresultoftheseexpeditionswasthedeterminationthattheglobeisoblatelyspheroidal。
Agreatcontemporaryandfellow-countrymanofLacaillewasJeanLeRondd’Alembert1717-1783，who，althoughnotprimarilyanastronomer，didsomuchwithhismathematicalcalculationstoaidthatsciencethathisnameiscloselyconnectedwithitsprogressduringtheeighteenthcentury。D’Alembert，whobecameoneofthebest-knownmenofscienceofhisday，andwhoseserviceswereeagerlysoughtbytherulersofEurope，beganlifeasafoundling，havingbeenexposedinoneofthemarketsofParis。Thesicklyinfantwasadoptedandcaredforinthefamilyofapoorglazier，andtreatedasamemberofthefamily。Inlateryears，however，afterthefoundlinghadbecomefamousthroughoutEurope，hismother，MadameTencin，sentforhim，andacknowledgedherrelationship。Itismorethanlikelythatthegreatphilosopherbelievedherstory，butifsohedidnotallowherthesatisfactionofknowinghisbelief，declaringalwaysthatMadameTencincould\"notbenearerthanastep-mothertohim，sincehismotherwasthewifeoftheglazier。\"