Inthevacationwewentonlongeroutingsbymeansofourbicycles.InthiswaywecoveredmuchgroundinAuvergneandintheCevennesandvisitedseveralregionsattheseashore.Wetookagreatdelightintheselongall-dayexcursions,arrivingatnightalwaysinanewplace.Ifwestayedinoneplacetoolong,myhusbandbegantowishtogetbacktothelaboratory.ItisalsoinvacationtimethatwevisitedoncemyfamilyintheCarpathianmountains.MyhusbandlearnedsomePolishinviewofthisjourneytoPoland.
Butfirstofallinourlifewasourscientificwork.Myhusbandgavemuchcaretothepreparationofhiscourses,andIgavehimsomeassistanceinthis,which,atthetime,helpedmeinmyeducation.However,mostofourtimewasdevotedtoourlaboratoryresearches.
Myhusbanddidnotthenhaveaprivatelaboratory.Hecould,tosomeextent,usethelaboratoryoftheschoolforhisownwork,butfoundmorefreedombyinstallinghimselfinsomeunusedcornerofthePhysicsSchoolbuilding.Ithuslearnedfromhisexamplethatonecouldworkhappilyeveninveryinsufficientquarters.Atthistimemyhusbandwasoccupiedwithresearchesoncrystals,whileIundertookaninvestigationofthemagneticpropertiesofsteel.Thisworkwascompletedandpublishedin.
Inthatsameyearthebirthofourfirstdaughterbroughtagreatchangeinourlife.Afewweekslatermyhusband'smotherdiedandhisfathercametolivewithus.WetookasmallhousewithagardenattheborderofParisandcontinuedtooccupythishouseaslongasmyhusbandlived.
ItbecameaseriousproblemhowtotakecareofourlittleIreneandofourhomewithoutgivingupmyscientificwork.Sucharenunciationwouldhavebeenverypainfultome,andmyhusbandwouldnoteventhinkofit;heusedtosaythathehadgotawifemadeexpresslyforhimtoshareallhispreoccupations.Neitherofuswouldcontemplateabandoningwhatwassoprecioustoboth.
Ofcoursewehadtohaveaservant,butIpersonallysawtoallthedetailsofthechild'scare.WhileIwasinthelaboratory,shewasinthecareofhergrandfather,wholovedhertenderlyandwhoseownlifewasmadebrighterbyher.Sothecloseunionofourfamilyenabledmetomeetmyobligations.Thingswereparticularlydifficultonlyincaseofmoreexceptionalevents,suchasachild'sillness,whensleeplessnightsinterruptedthenormalcourseoflife.
Itcanbeeasilyunderstoodthattherewasnoplaceinourlifeforworldlyrelations.Wesawbutafewfriends,scientificworkers,likeourselves,withwhomwetalkedinourhomeorinourgarden,whileIdidsomesewingformylittlegirl.Wealsomaintainedaffectionaterelationswithmyhusband'sbrotherandhisfamily.ButIwasseparatedfromallmyrelatives,asmysisterhadleftPariswithherhusbandtoliveinPoland.
Itwasunderthismodeofquietliving,organizedaccordingtoourdesires,thatweachievedthegreatworkofourlives,workbegunabouttheendofandlastingformanyyears.
Ihaddecidedonathemeformydoctorate.MyattentionhadbeendrawntotheinterestingexperimentsofHenriBecquerelonthesaltsoftheraremetaluranium.Becquerelhadshownthatbyplacingsomeuraniumsaltonaphotographicplate,coveredwithblackpaper,theplatewouldbeaffectedasiflighthadfallenonit.Theeffectisproducedbyspecialrayswhichareemittedbytheuraniumsaltandaredifferentfromordinaryluminousraysastheycanpassthroughblackpaper.Becquerelalsoshowedthattheserayscandischargeanelectroscope.Heatfirstthoughtthattheuraniumrayswereproducedasaresultofexposingtheuraniumsalttolight,butexperimentshowedthatsaltskeptforseveralmonthsinthedarkcontinuedthepeculiarrays.
MyhusbandandIweremuchexcitedbythisnewphenomenon,andIresolvedtoundertakethespecialstudyofit.Itseemedtomethatthefirstthingtodowastomeasurethephenomenonwithprecision.InthisIdecidedtousethatpropertyoftherayswhichenabledthemtodischargeanelectroscope.However,insteadoftheusualelectroscope,Iusedamoreperfectapparatus.OneofthemodelsoftheapparatususedbymeforthesefirstmeasurementsisnowintheCollegeofPhysiciansandSurgeonsinPhiladelphia.
Iwasnotlonginobtaininginterestingresults.Mydeterminationsshowedthattheemissionoftheraysisanatomicpropertyoftheuranium,whateverthephysicalorchemicalconditionsofthesaltwere.Anysubstancecontaininguraniumisasmuchmoreactiveinemittingrays,asitcontainsmoreofthiselement.
Ithenthoughttofindoutiftherewereothersubstancespossessingthisremarkablepropertyofuranium,andsoonfoundthatsubstancescontainingthoriumbehavedinasimilarway,andthatthisbehaviordependedsimilarlyonanatomicpropertyofthorium.IwasnowabouttoundertakeadetailedstudyoftheuraniumandthoriumrayswhenIdiscoveredanewinterestingfact.