ABSTRACTS OF TECHNICAL ARTICLES 727 



2. The noon value of ionic density of the E and Fi region attained a 

 maximum in summer and a minimum in winter whereas the reverse 

 condition, of minimum in summer and maximum in winter, was found 

 for the F2 region. 



3. The time of maximum ionic density of the F2 region varied with 

 the seasons of the year, occurring near noon in winter and near sunset 

 in summer. 



The paper also shows a series of virtual height contour maps for the 

 four seasons of the year. 



Utilization of Electrical Resistance Measurements for Controlling the 

 Composition of Alloys.^ E. E. Schumacher and L. Ferguson. To 

 stimulate interest in the more general use of the electrical resistance of 

 solid solutions for indicating the composition of alloys, details con- 

 cerning one application are set forth in this paper. While for other 

 systems certain elements of the method as outlined here might have 

 to be modified, it appears that the general principle could be ad- 

 vantageously utilized in many instances. This paper presents, 

 therefore, a practical resistance method of supplementing ordinary 

 chemical analyses in the determination of the antimony content of 

 lead-antimony alloys ranging at least from 0.4 to 1.1 per cent. It has 

 been found that, within this range, a 1 per cent change in resistance is 

 produced by a change in antimony content of less than 0.1 per cent 

 and that the maximum deviation in resistance data may reasonably 

 be made so small as to correspond to not more than ±0.01 per cent 

 antimony. 



* Metals and Alloys, June, 1935. 



