TransactionsPublished under the care of the General Secretary and the Treasurer . , therefore, the amount of emana-tion present in the exposing chamber during the first exposure wasabout twice that remaining in the gas when the second took result leads to the conclusion that the amount of excited radio-activity produced in any case is directly proportional to the amountof emanation present, which is in accordance with the deductionsof Eutherford and other investigators from their experiments witliactive emanations from radium and thorium. As the numbers in Column IV show, a consider
TransactionsPublished under the care of the General Secretary and the Treasurer . , therefore, the amount of emana-tion present in the exposing chamber during the first exposure wasabout twice that remaining in the gas when the second took result leads to the conclusion that the amount of excited radio-activity produced in any case is directly proportional to the amountof emanation present, which is in accordance with the deductionsof Eutherford and other investigators from their experiments witliactive emanations from radium and thorium. As the numbers in Column IV show, a considerable amount ofactivity was concentrated upon the rod when positively this exposure, the rod was connected to the positive terminalof a Toepler-Holtz machine with its negative Joined to earth. The 15. Rutherford Radioactivity, Chap. IX, p. 255. 420 McLEXXAX: RADIOACTIVITY OF GASES. polarity of the machine was examined from time to time duringthe experiment bitt no indication of the occurrence of a reversalwas observed. The experiment was repeated upon a number of. Fig. 7. different occasions and the rod was always found to possess a smallbut well-marked activity after an exposure in the gas positivelycharged. The result was checked by exposing the rod positively McLennan: radioactivity of gases. 421 charged in a second receiver which contained only ordinary air, butin this test no trace of radioactivity was observed. Allowing a deflection of 11 divisions per minute for the so-called spontaneous ionization, it will be seen from the numbersgiven in Table IX. that the activity excited under positive exposurewas about one-half that obtained with the uncharged rod and about15 per cent of that obtained with negative electrification. A num-ber of exposures made, first under negative electrification and thenunder positive, showed this ratio to be fairly constant. The concentration of excited radioactivity upon positively chargedconductors exposed in the open air has been
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