Abstracts of Bell System Technical Papers Not 

 Appearing in this Journal 



Influence of Carbon and Silicon Variations in Grey Cast Iron} D. G. 

 Anderson and G. R. Bessmer. In this short article the author gives 

 the results of a series of tests of grey cast irons with different carbon 

 and silicon contents. Three series were run in each of which the 

 silicon content was kept constant and the amount of carbon varied. 

 The results indicated that with two percent silicon the carbon content 

 may be reduced without materially increasing the amount of com- 

 bined carbon. This results in some improvement in the physical 

 properties of the iron. 



Strength-Tests of Telephone Materials.- J. R. Townsend. Static 

 tests, such as the ordinary tension or torsion tests, have fallen some- 

 what into disrepute during the last ten years, the author claims, as 

 the ultimate strengths obtained from them are not always indicative 

 of the forces materials will withstand in actual service. Their place 

 is being taken by repeated-stress tests in which the sample is sub- 

 jected to conditions more nearly representing those met in ordinary 

 service. In illustration the author mentions several tests of this class 

 being applied in Bell Telephone Laboratories on cable sheath material 

 and springs. 



The Reduction of Atmospheric Disturbances .^ John R. Carson. In 

 the decade or so during which the problem of eliminating or at least 

 reducing atmospheric disturbances has been given serious and syste- 

 matic study we have learned, more or less definitely, what we can and 

 cannot do in this direction. For example, we know that there are 

 definite limits to what can be accomplished by frequency selection. 

 We know that directional selectivity is of substantial value, particularly 

 when the predominant interference comes from a direction other than 

 that of the desired signal, and we can calculate pretty well the gain to 

 be expected from a given design. 



The object of this note is to analyze another arrangement which 

 provides for high-frequency selection plus low-frequency balancing 

 after detection. The broad idea of balancing out the interference is 

 old, but no general analysis of the arrangement seems to have been 

 made. Furthermoie the principle of balance has recently acquired 



1 "Fuels and Furnaces," Vol. VI, No. 7, pp. 957 and 972, July, 1928. 



2 "Instruments," Vol. 1, No. 7, pp. 313-315, July, 1928. 



^Proceedings of the Institute of Radio Engineers, July, 1928, \'ol. 16, No. 7, pp. 

 966-975. 



808 



