ABSTRACTS OF TECHNICAL ARTICLES 187 



same for the same time of year on different years. These undisturbed 

 transmission conditions are presented by "normal" surfaces. Com- 

 parison of these surfaces shows that the higher frequencies are less 

 attenuated in winter. Reception on the highest frequency, 27 mc 

 was best in winter; in summer this frequency was never heard. 



The effect of solar disturbances on short-wave transmission is to 

 reduce reception on all frequencies. Sometimes the higher frequencies 

 are the more adversely affected. Some of the possible causes of these 

 disturbances are discussed. 



From the measurements made on "static" at New Southgate, 

 data on the variation of its field strength as a function of frequency, 

 time of day, and season are given. 



Methods of High Temperatitre Treatment.^ Paul P. Cioffi. The 

 object of this paper is to describe methods which have been developed 

 in this laboratory for treating metals, chiefly iron and its alloys, at 

 all temperatures up to about 1700° C, considerably above the melting 

 point of iron, and in any atmosphere ranging in pressure from 10"^ 

 mm. of mercury to 20 or more atmospheres. The methods of heating, 

 and the forms of the materials heated fall into three rather well- 

 defined groups: (1) Long wires and tapes heated to any temperature 

 up to a few degrees below the melting point by passing currents 

 through them in the presence of a gas (a) under a pressure of one 

 atmosphere or less, or {b) under a pressure up to 20 atmospheres. 

 (2) Toroids heated by induction in a gas atmosphere, with the gas 

 pressure ranging from 10-« mm. to one atmosphere. (3) Any shape 

 of specimen heated up to about 1700° C. in a molybdenum wound 

 furnace in a gas pressure ranging from 10"^ mm. to 20 atmospheres. 



In investigations dealing with the effect of heat treatment on the 

 properties of materials, the temperature range covered, often limited 

 by the lack of suitable facilities, is likely to obscure important or 

 interesting effects produced by heat treatments at high temperatures. 

 The new high values of the magnetic permeability of iron recently 

 reported were made possible by employing the methods here described ; 

 in fact, these methods were all developed in connection with the 

 investigation of the magnetic properties of materials as dependent 

 upon temperature and time of heat treatment and rate of cooling in 

 any atmosphere. These methods are also applicable to other metals 

 which can be shaped into long wires or tapes or toroids. 



^ Jour. Franklin Institute, November, 1931. 



