. The Bell System technical journal . and F. W. Aston reveal the charge-to-mass ratios of ionsoccurring in a gas carrying a self-maintaining discharge, but give verylittle information about the precise conditions necessary to producethem. A combination of methods of these two kinds was first effectedby H. D. One of the tubes employed by Smyth is sketched in Fig. 3. Electronsfrom the filament Fare accelerated through the potential-rise Fi to the ^ For work published up to 1922 sec the review and bibliography by A. J. Saxton,Phil. Mag. 44, pp. 809-823 (1922). See also J. T. Tate, Phxs.
. The Bell System technical journal . and F. W. Aston reveal the charge-to-mass ratios of ionsoccurring in a gas carrying a self-maintaining discharge, but give verylittle information about the precise conditions necessary to producethem. A combination of methods of these two kinds was first effectedby H. D. One of the tubes employed by Smyth is sketched in Fig. 3. Electronsfrom the filament Fare accelerated through the potential-rise Fi to the ^ For work published up to 1922 sec the review and bibliography by A. J. Saxton,Phil. Mag. 44, pp. 809-823 (1922). See also J. T. Tate, Phxs. Rev. (2) 23, pp. 293-294 (1924). ^Proc. Roy. Soc. A102, pp. 283-293 (1922-23); A104, pp. 121-134 (1923); (2) 25, pp. 452^68 (1925) and references there given. SOME J/)//./.V(7:.V /.V IHYSICS^M 473 gauze El, and then turned back by an adxerse potential-fall Vo beforethey reach the partition Eo pierced by the slit ^2. Positive ions pro-duced bv the electrons in the region between £1 and Eo are drawn ...^ \. !.^^^^^s^^^^^^^^■^■.■^^^^^^^^s^^^^^■^^ Fie. 3 toward Eo; some of them emerge through S2, and encounter an addi-tional potential-fall Vz which draws them to the partition E^. Thosewhich pass through the slit S3 are now ready, after passing through the 474 BELL SYSTEM TECHNICAL JOURNAL field-free region R, to be swung around in senii-circular arcs by a mag-netic field i7 applied normally to the plane of the paper over the regionQ; thus they arrive at the ion-collector behind the slit Si. The majorexperimental difficulty consists in maintaining simultaneously a gas-density between F and Eo high enough to afford plenty of ions, and agas-density in R and Q low enough so that the ion-stream is not dis-persed. This is effected by feeding in the gas through A and applyingpowerful pumps to draw it out through B, C and D. Varying H and plotting against it the current into the ion-collector,one obtains a curve with peaks, such as the one in
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