ABSTRACTS OF TECHNICAL ARTICLES 857 



Maximum Exairsion of the Photoelectric Long Wave Limit of the 

 Alkali Metals J Herbert E. Ives and A. R. Olpix. Earlier experi- 

 ments have shown that the long wave limit of photoelectric action in 

 the case of thin films of the alkali metals varies with the thickness of 

 the film. A maximum value is attained greater than that for the 

 metal in bulk, which for the majority of the alkali metals lies in the 

 infra-red. The wave-length of the maximum excursion of the long 

 wave limit was first studied for Na, K, Rb and Cs. In each case it 

 was found to coincide with the first line of the principal series, 

 i.e., the resonance potential. If this relation holds for lithium, its 

 maximum long wave limit should be greater than that of sodium. 

 This was tested and confirmed by experiments in which red-sensitive 

 lithium films were prepared, sensitive to 0.6708 ^l. It is suggested 

 that photoelectric emission is caused when sufficient energy is given 

 to the atom, to produce its first stage of excitation. The identity of 

 photoelectric and thermionic work functions suggests that atomic 

 excitation is the initial process in thermionic emission as well. 



Magnetic Testing Furnace for Toroidal Cores.^ G. A. Kelsall. 

 When making magnetic tests at high temperatures trouble is often 

 experienced in maintaining the insulation between turns of the mag- 

 netizing and exploring windings and between the windings and the 

 test sample. 



This paper describes a magnetic testing furnace for toroidal speci- 

 mens which eliminates these difficulties. By means of this furnace 

 the test sample may be passed through a definite temperature cycle 

 and the variation in magnetization for a constant magnetizing force 

 determined or the temperature may be held constant while measure- 

 ments are made for the B-H curve or for a hvsteresis loop. 



Electrical Wave Analyzers for Power and Telephone Systems.^ R. G. 

 McCuRDY and P. W. Blye. This paper describes two types of 

 electrical analyzers which have been developed for the direct measure- 

 ment of harmonic components of voltage and current on power and 

 telephone systems. These devices are assembled mechanically in a 

 form suitable for use either in the laboratory or in the field. Both 

 instruments, which differ chiefly with respect to sensitivity and input 

 circuit arrangement, employ multistage vacuum tube amplifiers and 

 two duplicate interstage selective circuits. 



''Physical Review, Vol. 34, July 1, 1929, pp. 117-128. 



'^Journal of the Optical Society of America and Review of Scientific Iiistninioits, 

 Vol. 19, July, 1929, pp. 47-49. 



M. /. E. E. Journal, Vol. 48, June, 1929, pp. 461-464 (abridgment). 



