. The London, Edinburgh and Dublin philosophical magazine and journal of science. ^1 CO CO H ll oco^cprH©CM-t 01 t- ib -A* cb Ah -A as iA -A< iA CM cb • l^CO«COCCO*^^tlTt<C0 01rH -^OlCNr-H 1 M M M M M M M ! :i§ ; § 1 ::::::::::::: °2 « S * _ Aj 1 g « g 0 « TS 03 03 y r- O P3 j pqpH<jpHC»9tti95 s>d do cb l^ A* as 1^ 0 cb do 0 cm r- cmSo 1 © O OS OS ^h © CO CO O O CO CM ^h Reflexion of the fi-P articles by Matter. 861 deposits of thorium or of radium emanation, the percentageof the reflected /3-particles rose to a maximum but finallydecreased. The results with the thorium activ
. The London, Edinburgh and Dublin philosophical magazine and journal of science. ^1 CO CO H ll oco^cprH©CM-t 01 t- ib -A* cb Ah -A as iA -A< iA CM cb • l^CO«COCCO*^^tlTt<C0 01rH -^OlCNr-H 1 M M M M M M M ! :i§ ; § 1 ::::::::::::: °2 « S * _ Aj 1 g « g 0 « TS 03 03 y r- O P3 j pqpH<jpHC»9tti95 s>d do cb l^ A* as 1^ 0 cb do 0 cm r- cmSo 1 © O OS OS ^h © CO CO O O CO CM ^h Reflexion of the fi-P articles by Matter. 861 deposits of thorium or of radium emanation, the percentageof the reflected /3-particles rose to a maximum but finallydecreased. The results with the thorium active deposit aregiven in Table VI. and shown graphically in fig. 4. Table active deposit. Aluminium Percentage of in mms. reflected /3-particles. 0-045 65-3 •104 77-0 •163 796 •222 800 •340 760 •399 74-0 •458 73-0 •635 71-0 The first column gives the absorbing aluminium in the second column gives the percentage of reflected/3-particles. Fig. •oio •0?0 030 -040 -050 -060 Thickness of /?lum/n/um //v cms 070 This decrease may be due to one of two possible factors,viz., either the softer reflected rays are absorbed more thanis accounted for by the correction or the amount of reflexion,as measured by the ionization, increases with the velocity ofthe /3-particles only up to a certain velocity, after which itdecreases again. Since this investigation deals with theheterogeneous rays from radioactive bodies, and not with thepure rays of any one velocity, this point cannot be answeredhere definitely. Investigation of this special phase of theproblem is, however, now in progress (see following paperby Kovarik and W. Wilson). 862 Dr. A. F. Kovarik on the Absorption and Multiple Reflexion. Since the /3-particles are reflected from a substance intowhich they penetrate, the reflected rays should in turn bereflected it* a substance is placed in their path. Suppose wehave two parallel plates of lead and /3-particles of the typepair Ra
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