ABSTRACT
Radioactivesourceswereinadequate,therefore,toprobedeeperinto thenucleus.Moreenergeticandintensegeneratorsofparticleswere required.Acceleratorswereintheirinfancyinthe1920s,andwerenot tomakesignificantcontributionstotheproblemsofelementaryparticles untilthelate1940s.Therefore,physiciststurnedtothenaturalsourceof veryhigh-energyparticles,cosmicrays.
