ABSTRACTS OF TFXllSUAL ARTICLES 127 



urging the electronics engineer to improve old devices and to originate 

 new ones, and each time the efforts of the latter have been rewarded with 

 success the fruits of his work have been immediately applied to produce 

 new and more startling miracles of long-distance communication. 



Because of the close relationship of electronics and communications it is 

 necessary in reviewing the progress of the last decade to keep in mind that 

 it is progress in electronics and not in communications which is our theme. 

 It will be necessary to survey the trends in communications during the 

 period under review, but then it will be necessary to ask to what extent the 

 progress which has been made is due to advances in the electronic field and 

 what advances in the electronic devices themselves have laid the founda- 

 tion of this progress. There has been no attempt made to make this re- 

 view comprehensive in the sense that it include all items of progress which 

 are of individual interest. To do so would make it merely a catalog of 

 these many advances and an index to the periodical literature of the sub- 

 ject. Rather the object has been to trace the most significant trends of 

 development in the various fields and to emphasize those lines of advance 

 which appear to be most closely related to the general direction of progress 

 in the several fields of electrical communication. 



The Location of Hysteresis Phenomena in Rochelle Salt Crystals.^ W. P. 

 Mason. Measurements of the elastic properties of an unplated crystal, 

 the piezoelectric constant fi4, and the clamped dielectric constant of a 

 Rochelle salt crystal show that practically all hysteresis and dissipation 

 effects are associated with the clamped dielectric properties of the crystal. 

 A theoretical formulation of the equations of a piezoelectric crystal has 

 been made which takes account of the dissipation effects. The formulation 

 is given for the polarization theory. The frequency variation of the 

 clamped dielectric constant when interpreted by Debye's theory of dielec- 

 trics, modified to take account of hysteresis losses, indicates that there are 

 two components, one of which has associated with it a high viscous re- 

 sistance, whereas the other one does not. The non-viscous component 

 has a dielectric constant of about 100 at 0°C and is probably due to the 

 displacement of the ions in the lattice structure. The viscous component 

 has a dielectric constant of about 140 at 0°C and is probably due to the 

 dipoles of the Rochelle salt. Both components have higher dielectric 

 constants and hysteresis between the Curie points indicating a coopera- 

 tive action of the molecules for both components in this temperature region. 



A New Broadcast-Transmitter Circuit Design for Frequency Modulation!' 

 J. F. Morrison. The problem of generating wide-band frequency-modu- 



^ Phys. Rev., October 15, 1940. 

 ^ Proc. I.R.E., October 1940. 



