386 AUSTIN: CRYSTAL CONTACT DISTURBANCE PREVENTER 



by Abbot and Fowle and by Kimball, if we assume that for 

 small changes in radiation, the evaporation is directly. proportional 

 to the radiation received. In this connection, it should be re- 

 called that the pyrheliometer measurements deal only with the 

 direct rays of the sun. Since the scattered radiation would be 

 proportionately somewhat increased b}'^ the dust, the actual re- 

 duction in radiant energy during 1912 was probably not quite 

 so great as indicated by the solar measurements. This would 

 tend to bring the results more nearly in accord with the evapora- 

 tion measurements. 



In addition to measurements of the energy of the direct solar 

 beam. Abbot and Fowle* have also measured the total sky ra- 

 diation and the absorbed radiation. In former years, the sum of 

 the three parts of the solar radiation has found to fall below the 

 value of the solar constant by not more than 0.05 calorie. Their 

 measurements in 1912, however, show an outstanding difference 

 of about 0.28 calorie, which they attribute to the greater diffuse 

 reflection of the atmosphere resulting from the haziness. This 

 amounts to a reduction in the intensity of the solar radiation at 

 the earth's surface of about 10 per cent, a value which is in good 

 agreement with the observed diminution in evaporation. The 

 reduction in the mean evaporation at the 15 observing stations 

 following the haze of 1912 thus appears to afford an approximate 

 measure of the reduction in the intensity of the solar radiation 

 at the earth's surface. 



RADIOTELEGRAPHY. — A crystal contact disturbance preventer 

 for radiotelegraphic receiving. L. W. Austin, U. S. Naval 

 Radiotelegraphic Laboratory. 



In 1908 I published the results of a study of the rectifying 

 action of certain contacts, silicon-steel, carbon-steel, and tellur- 

 ium-aluminum. Soon after this it occurred to me that the prop- 

 erty of rapid change of resistance with impressed voltage shown 

 by these contacts, might be made use of in shunting to earth 

 loud interfering signals and atmospheric disturbances, so trouble- 



^ loc. cit., p. 13. 



