ABSTRACT
InsettingthestageforMoseley'sepochalcontribution,weare mindfulofthediscoverybyBarkla[18-1]andCharlesASadlerin 1907thatx-raytargetsgiveoffdiscretelinesofsecondaryradiation-- radiationasdistinctlycharacteristicofthetargetelementasarelines initsopticalspectrum.The'hardness'ofthecharacteristicradiation increasedregularlywithascendingplacementoftheelementsinthe periodictable-thefactorexploitedsosuccessfullybyMoseley.
