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BELL SYSTEM TECHNICAL JOURNAL 



mean speed co of the electrons by Langmuir's method — it was a wire 

 stretching clear across the globular tube, being made of this form so 

 that it might give average values appropriate to the whole of the 

 discharge. The best of his data refer to neon-helium mixture at 

 various pressures of the order of a few tenths of a millimeter; there 

 are data also for argon and nitrogen. 



From equation (16), k should be proportional to A^" so long as Wo 

 does not depart too much from 1 and other things remain unchanged. 

 Hasselbeck varied N by varying the current maintaining the ionization, 

 measured it with the probe and measured the absorption. So long 

 as the pressure of the gas was below a certain value, of slightly over 

 0.1 mm. Hg, the curves of ^ vs iV were indeed straight lines rising from 

 the origin (Fig. 8), though at higher pressures they were concave- 

 upward. As for the curves of absorption vs frequency, some display 



^ • 



6 



N X 10" 



Fig. 8 — Showing the proportionality of absorption of Hertzian waves to number 

 of free electrons per cc. of absorbing gas (neon-helium mixture, pressure 0.18 mm. 

 Hg). (W. Hasselbeck; Annalen der Physik.) 



maxima in the range over which they are plotted, some do not; but it 

 is possible to suppose that each is characterized by a single maximum, 

 which moves toward higher frequencies when the pressure or the 

 ionization is augmented, and in some of Hasselbeck's experiments 

 happened to be out of the range. 



The comparison of the absorption-z;5. -frequency curves with so 

 complicated an expression as that of equation (17) is no simple matter, 

 nor is Hasselbeck's description of his procedure entirely clear. It 

 appears, however, that the curves obtained in neon-helium mixture 

 at a pressure of 0.87 mm. Hg depart but little from the form of the 

 expression on the right of (17), and that what departure there is 

 may not be significant. However the curves obtained at the much 



