ABSTRACTS OV BELL SYSTEM TECIIXICAL PAPERS 217 



A Contribution to the Theory of Ferromagnetism. L. W. McKeehxn.-'' 

 Relation of permeability and hysteresis to atomic magnetostriction. — 

 In permalloy, it has been found that magnetostriction changes sign at 

 about 81 per cent. Ni, hysteresis losses can be made vanishingly 

 small near this composition, and these effects are not due to the special 

 alignment of crystals. It is suggested that in every ferromagnetic 

 material the process of magnetization involves (1) intra-atomic 

 changes, presumably changes in the orientation of electron orbits, 

 governed by quantum dynamics and independent of environment; 

 and (2) inter-atomic changes (stresses and strains). The inter- 

 dependence of the inter-atomic changes and the intra-atomic changes 

 is conveniently described as atomic magnetostriction. On this view, 

 hysteresis loss and magnetic hardness are due to the energy required 

 to produce, in succession, the local deformations associated with 

 changes in the magnetization of single atoms or small groups of atoms. 

 High initial permeability and low hysteresis loss in permalloy are 

 explained as resulting from locally compensatory atomic magneto- 

 strictions of the nickel and iron atoms in small groups. The funda- 

 mental differences in the magnetic behavior of Fe, Ni and Co are 

 attributed to differences in their atomic magnetostrictions. Other 

 differences are attributed to differences in the mechanical proper- 

 ties which alter the energy expended when atomic magnetostriction 

 takes place. 



Induction from Street Lighting Circuits: Effects on Telephone Circuits. 

 R. G. McCuRDY.^ Synopsis. — This paper discusses series street 

 lighting circuits from the point of view of their relations to nearby 

 telephone circuits. These lighting circuits often have a much greater 

 inductive influence in proportion to the amount of power transmitted 

 than have most other types of power distribution or transmission 

 circuits. This is due to the relatively large distortion in wave shape of 

 voltage and current on certain types of these lighting circuits, and to 

 the unbalanced voltages to ground which occur with series layouts. 

 Three general types of lighting circuits are discussed. These are a-c, 

 arc circuits, d-c, arc circuits supplied by mercury arc rectifiers, and 

 alternating-current incandescent circuits. Of these, the incandescent 

 type of circuit, in which the lamps are equipped with individual 

 series transformers or auto-transformers, is the most important in 

 this respect. Measures for reducing interference from these circuits 

 are discussed. 



= Physical Review, Vol. 26, No. 2, Aug., 1925. 



^A. I. E. E. Journal, Vol. 44, pp. 1088-1094, Oct., 1925. 



