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RANGEFia. 2. Feather plot for Ca&, I.O 12,000 counts per minute, and the contribution due to gamma-rays and other unabsorbed contaminants was less than one part in 3000 with the strongest source, thus indicating the absence of any appreciable amount of gamma-radiation.The absorption curve obtained with the strongest source is shown in Fig. 1.The Feather plot, shown in Fig. 2, gives a range of 64+1 mg/cm'.Glendenin' has shown that a reliable range-energy curve for the low energy region can be derived from the data of Marshall and %'ard' for monoenergetic electrons and beta- ray spectrograph data on low energy beta-emitters.Glen- denin's curve is identical with that of Marshall and Nard below 0.5 Mev.Using this range-energy curve, we have found that the Ca~beta-radiation has a maximum energy of 260+5 kev.%'e have found no evidence of any harder beta-radiation, or of any gamma-radiation at all in the course of this investigation.'Ackeomledgesents.-This work has been
Julian Schwinger (Sun,) studied this question.