CONTEMPORARY ADVANCES IN PHYSICS 607 



References 



The theory underlying equations (1) to (4) is well known ; it is given in considerable 

 detail by G. Mierde'l, Ann. d. Phys., 85, 612-640 (1928), with some illustrative 

 curves, and in several other papers. The theory underlying equations (5) to (10) 

 apparently originated, like so much else in electronics, with 11. A. Lorentz; it was 

 developed with especial reference to the transmission of radio waves by W. H. 

 Eccles, Proc. Roy. Soc, A 87, 79-99 (1912); later enunciations, with various modifi- 

 cations, may be found in the papers of J. Salpeter, Phys. ZS., 14, 201-203 (1913); 

 E. V. Appleton & F. W. Chapman, Proc. Phys. Soc. Land., 44, 246-254 (1932), 

 and in several papers cited in the next paragraph. 



Experiments designed to measure dielectric constant and conductivity of ionized 

 gas for high-frequency fields have been performed by A. Szekely, Ann. d. Phys. (5), 

 3, 112-132 (1929); E. V. Appleton & E. C. Childs, Phil. Mag. (7), 10, 969-994 

 (1930); Appleton & Chapman, I.e. supra; E. C. Childs, Phil. Mag. (7), 13, 873-887 

 (1932); H. Gutton, Annales de physique (10), 13, 62-129 (1930); H. Gutton & J. 

 Clement, C. R., 184, 441-443, 676-678 (1927); V. Jonescu & C. Mihul, C. R., 192, 

 343-345 (1931.) 



Experiments on the absorption of Hertzian waves by ionized gases: H. Danzer, 

 Ann. d. Phys. (5), 2, 27-62 (1929); W. Hasselbeck, ibid. (5), 12, 477-502 (1932). 



Experiments on the reaction of electron-streams projected through very rarefied 

 gas to a high-frequency field: L. Bergmann & W. During, Ann. d. Phys. (5), 1. 

 1041-1068 (1929); S. Benner, ibid. (5), 3, 993-996 (1929) (theory); V. Jonescu & 

 C. Mihul, C. R., 191, 1436-1438 (1930). 



Equation (24) for the so-called "plasma-electron" natural frequency appears to 

 have been first derived by J. J. Thomson, and shortly afterward by L. Tonks & 

 I. Langmuir, Phys. Rev. (2), 33, 195-210, 990 (1929); see also Thomson, Phil. Mag. 

 (7), 11, 697-735 (1931). Experiments on this, and natural frequencies of possibly 

 different origin: L. Tonks, Phys. Rev. (2), 37, 1458-1483 (1931); H. Gutton, Annales 

 de physique (10), 13, 62-129 (1930); C. Gutton, ibid. (10), 14, 5-14 (1930); Appleton 

 & Chapman, I.e. supra. 



Natural frequency or frequencies appearing when a constant magnetic field is 

 imposed upon the gas: S. Benner, Naturwiss. 17, 120-121 (1929); Appleton & Chap- 

 man, H, Gutton, L. Tonks, ll.cc. supra. The influence, upon the transmission of 

 radio waves, of the magnetic field of the earth, was inferred independently in America 

 by H. W. Nichols & J. C. Schelleng, Bell Syst. Tech. Jl., 4, 215-234 (1925) and 

 in England by E. V. Appleton & M. A. F. Barnett, Electrician, 94, 398 (1925). 



