ABSTRA CTS OF TECHNICA L A RTICLES 391 



The Molecular Beam Magnetic Resonance Method. The Radiofrequency 

 Spectra of Atoms and Molecules.^ J. B. M. Kellogg and S. Millman. A 

 new method known as the "Magnetic Resonance Method" which makes 

 possible accurate spectroscopy in the low frequency range ordinarily known 

 as the "radiofrequency" range was announced in 1938 by Rabi, Zacharias, 

 Millman, and Kusch (R6, R5). This method reverses the ordinary pro- 

 cedures of spectroscopy and instead of analyzing the radiation emitted by 

 atoms or molecules analyzes the energy changes produced by the radiation 

 in the atomic system itself. Recognition of the energy changes is accom- 

 plished by means of a molecular beam apparatus. The experiment was 

 first announced as a new method for the determination of nuclear magnetic 

 moments, but it was immediately apparent that its scope was not limited 

 to the measurement of these quantities only. It is the purpose of this 

 article to summarize the more important of those successes which the 

 method has to date achieved. 



Metal-Lens Antennas.^ Winston E. Kock. A new type of antenna is 

 described which utilizes the optical properties of radio waves. It consists 

 of a number of conducting plates of proper shape and spacing and is, in 

 effect, a lens, the focusing action of which is due to the high phase velocity 

 of a wave passing between the plates. Its field of usefulness extends from 

 the very short waves up to wavelengths of perhaps five meters or more. 

 The paper discusses the properties of this antenna, methods of construction, 

 and applications. 



Underwater Noise Due to Marine Life}^ Donald P. Loye. The wide- 

 spread use of underwater acoustical devices during the recent war made 

 it necessary to obtain precise information concerning ambient noise condi- 

 tions in the sea. Investigations of this subject soon led to the discovery 

 that fish and other marine life, hitherto generally classified with the voiceless 

 giraffe in noisemaking ability, have long been given credit for a virtue they 

 by no means always practice. Certain species, most notably the croaker 

 and the snapping-shrimp, are capable of producing noise which, in air, 

 would compare favorably with that of a moderately busy boiler factory. 

 This paper describes some of the experiments which traced these noises to 

 their source and presents acoustical data on the character and magnitude 

 of the disturbances. 



Elastic, Piezoelectric, and Dielectric Properties of Sodium Chlorate and 

 Sodium Promote}^ W. P. Mason. The elastic, piezoelectric, and di- 



8 Rev. Mod. PItys., July 1946. 



^ Proc. I.R.E. and Waves and Electrons, November 1946. 



^^ Jour. Aeons. Soc. America, October 1946. 



iip/m. Rev., October 1 and 15, 1946. 



