478 BELL SYSTEM TECHNICAL JOURNAL 



in which transformers have been installed, they have prevented in- 

 terruption of the circuits not only for long periods but also for short 

 periods lasting only for the duration of a surge. 



On the Preparation of Iron and Steel Specimens for Microscopic 

 Investigations.^ Francis V. Lucas. A given lens system has certain 

 potential resolving powers. This potential resolving power may or 

 may not be fully realized in practice. Even a low power objective has 

 remarkable resolving ability and the very high aperture objectives are 

 capable of furnishing sharp brilliant images of details measuring about 

 two hundred atom diameters. 



The author describes in this paper methods and materials for the 

 critical preparation of iron and steel specimens. A flotation apparatus 

 which he has developed for the preparation of abrasives is described 

 and a typical particle size analysis of a magnesium oxide abrasive 

 prepared by this method is given. 



Some Alloys of Copper and Iron {The Tensile, Electrical and Corrosion 

 Properties)} Earle E. Schumacher and Alexander G. Souden. 

 Bars of copper-iron alloy 0.75 and 1.0 in. in diameter and 20 in. in 

 length were prepared with compositions ranging from 75 Cu-25 Fe to 

 37.5 Cu-62.5 Fe without segregation sufficient to detect by differences 

 in electrical and mechanical properties. These alloys were hot worked 

 satisfactorily to 0.25 in. rod. The copper-iron alloys in the range 

 investigated consist of a mixture of solid solutions of the constituent 

 elements, the phasial relationships of which depend on the thermal 

 treatment. 



A few of the observations made concerning these alloys are listed 

 below: 



1. The alloys in the range investigated are of the precipitation harden- 



ing type, but do not require a drastic quenching treatment to 

 retain a supersaturated iron-rich phase. The optimum com- 

 bination of tensile and electrical properties is obtained in the 

 50 copper-50 iron alloy by aging at 500° C. followed by hard 

 drawing. 



2. High tensile strengths associated with desirable electrical conduc- 



tivities can be developed for certain of the compositions. An 

 alloy of 50 Cu-50 Fe, for example, can be prepared in the No. 

 18 AWG with an ultimate strength of 180,000 to 190,000 lbs. 

 per sq. in. and an electrical conductivity of approximately 

 30 per cent. 



* Trans. Amer. Soc.for Metals, March, 1936. 

 6 Metals and Alloys, April, 1936. 



