ABSTRACTS OF RECENT TECHNICAL BOOKS 659 



Tension increases magnetostrictive contraction and diminishes 

 magnetostrictiv'c expansion. It causes a reversal in the sign of mag- 

 netostriction in permalloy with 80 per cent Ni, a small contraction 

 preceding the final small expansion. 



Transmission Features of Transcontinental TelephonyJ H. H. 

 Nance and O. B. Jacobs. In this paper, the various steps in the 

 establishment of the existing network of transcontinental type cir- 

 cuits and the transmission design considerations are reviewed. The 

 discussion covers the communication channels obtained from trans- 

 continental type facilities and the bands of frequencies employed, and 

 includes carrier-current systems, telephone repeaters and signalling 

 systems. Mention is made of special uses of transcontinental tele- 

 phone circuits, such as the transmission of program material for 

 broadcasting and the transmission of pictures. Finally, the main- 

 tenance methods required to keep the system at full efficiency are 

 outlmed. 



^ Presented at the Pacific Coast Convention of the A. I. E. E., Salt Lake City, 

 Utah, Sept. 6-9, 1926. 



