. The Bell System technical journal . ned the results in the hope of thuseliminating the effects both of the divergence of the beam in a vacuum,and of residual gases.^ It is not always easy to make out from a paper just what procedure the observerhas followed, nor how far he has traced the curves of Q vs. x or Q vs. N. CONTEMPORARY ADVANCES IN PHYSICS 677 (I pause to point out the relation between formula (8) and the earlierformula (1). The first two terms in the Taylor expansion of e~y being(1 — 3*), one may write instead of (8), <2 = <2o - Q^Nax, (10) which is formula (1).) The experim
. The Bell System technical journal . ned the results in the hope of thuseliminating the effects both of the divergence of the beam in a vacuum,and of residual gases.^ It is not always easy to make out from a paper just what procedure the observerhas followed, nor how far he has traced the curves of Q vs. x or Q vs. N. CONTEMPORARY ADVANCES IN PHYSICS 677 (I pause to point out the relation between formula (8) and the earlierformula (1). The first two terms in the Taylor expansion of e~y being(1 — 3*), one may write instead of (8), <2 = <2o - Q^Nax, (10) which is formula (1).) The experiment of Ramsauer acquired instant fame, because thedata which he got with argon were of a nature totally unexpected,^ andcaused immense surprise. His apparatus is a metal box, partitioned into chambers, the party-walls of which are pierced with slits delimiting a narrow path curved inthe form of a circle. Details are different in the different boxes whichhe used at various times, and in those which several other physicists— CM 5r-. Fig. 2—Ramsauers apparatus for measuring the cross-section for interception. {Physikal. Zeitschrifl.) Maxwell, Erode, and T. J. Jones among them—made after the patternof his; but a fair idea of all is given by Fig. 2. Photoelectrons ^^ escapefrom the metal plate at Z, and are accelerated to the speed desired by apotential-rise from Z to the walls of the box. The electron-beam con-sists of corpuscles sweeping around in circles so centred and so propor-tioned that they pass through all the slits. It is of course a magnetic ^^ This was first disclosed in Mayers paper from the same laboratory, but Mayeryields to Ramsauer the credit of having noticed it sooner. 11 Some of the American physicists used thermionic electrons instead; in certainexperiments the filament replacing Z is encased in a coaxial cylinder with a narrowslit, from which electrons escape after receiving the energy corresponding to the po-tential-rise from filament to cylinder. 678
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