ABSTRACTS OF TECHNICAL ARTICLES 273 



form at about 20 ohm-i-outimeters. Cunent of about one ampere flowed 

 on the copi)er jacket into the low resisti\-ity areas on eithei' side and was 

 found to be sustained l)y ])olarization effeets when the cathodic protection 

 current was removed. The current loss on the coi)])er jacket was found to 

 be concentrated in an area about 720 feet wide, 360 feet each side of the 

 point wheie the cathodic protection current had been drained from the 

 cop])er jacket. The copper jacket to soil ])otential tested most negative to a 

 co])per sulfate half cell in the 720-foot area where the current loss was con- 

 centrated and was of the order of —1.0 to —1.1 volts. Permanent remedial 

 measures will consist of installations of magnesium anodes distributed 

 tluoughout the low earth resistivity' area and insulating joints in the copper 

 jacket at locations wheie large changes in the earth resistivity occur. 



WiLLLX.MS, H. ,1.\ l{. M. BOZORTH^ AND M. (loERTZ' 



Mechanism of Transition in Magnetite at Low Temperatures, PHn^s. 

 Rev., 91, pp. 1107-1115, Sept. 1, 1953 (Monograph 2149). 



When magnetite is cooled through — 160°C it is known to undergo a transi- 

 tion (cubic to orthorhombic) that is influenced l)y the pi'esence of a mag- 

 netic field. Our experiments are in agreement with the following mechanism 

 of the transition : The orthorhombic c axis is parallel to one of the original 

 cubic axes and is the axis of easiest magnetization. Generally, different 

 regions of the original crj'stal will transform with their c axes lying along 

 different cubic axes, and when no field is applied there are 6 different orien- 

 tations which different regions assume. When a field is applied during a 

 cooling a c axis tends to lie along the original cubic axis that is nearest to the 

 applied field, the a and b axis having less but different tendencies to lie 

 parallel to the field. Six magnetic cr^-stal anisotrojjy constants are derived 

 from torque curves measured in the (100) and (110) planes. From them 

 magnetization curves ai-e calculated for the 100 and 110 dii-ections, and 

 these are in agreement with ex])eriment. 



Wood, E. X} and L. M. Towslky' 



Manganese Film-Shield for FeK X-Rays, Rev. 8ci. Instr., 24, p. 547, 

 July, 1953. 



1 Bell Telephone Laboratories. 



