252 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 11, NO. 11 



and directly as the intensity of the earth's magnetic field. 



Over sea the electrical conductivity of the air fluctuates less and 

 is more uniform from day to day than over land. 



Discontinuities in space and time. (Intensity and strays.)— It 

 is found that some stations have great difficulty in establishing com- 

 munication with other stations quite near them though they have 

 no difficulty in reaching other stations much farther away. Stations 

 in the neighborhood of Boston, Massachusetts, furnish examples of 

 this. It has also been found impossible to transmit over 70 miles 

 east from Hartford, Connecticut. 



Silent zones, where signals cannot be heard from certain stations, 

 are frequently found at sea, the most noted ones being along the 

 coast or between two bodies of land. 



Inland stations have been found to get copy when coastal stations 

 cannot. This may possibly be a sunset phenomenon or the result 

 of the location of the stations with respect to sources of strays. 



Stations less than a mile apart may differ radically in the intensity 

 of strays observed and in the intensity of signals received from a 

 given transmitting station. 



Meteorological effects. (Intensity, fading, strays.) — A good radio 

 night, that is, one when the signals are loud and the strays are weak, 

 is usually cloudy or is preceded by a cloudy day. Fading, however, 

 is not affected by clouds. Transmission is usually good during and 

 immediately after a rain storm. 



While correlations between meteorological and radio conditions 

 have been sought repeatedly, little proof of such correlations has 

 been found. 



Indirectly, meteorological conditions such as temperature, convec- 

 tion, etc., at the earth's surface may somewhat affect the regularity 

 of the boundary surface of the Heaviside or aurora layer, and may 

 thus cause night strays and the disappearance of signals. Thus the 

 difference in temperature between land and sea may cause an effect 

 extending far up into the air. 



The effect of weather conditions on the insulation of an antenna 

 and the resistance of the ground are principally important in day 

 transmission. The effect of weather conditions on ionization and 

 on the boundaries of the ionized regions in the upper atmosphere are 

 more prominent at night. 



During the October, 1920, fading tests conducted by the American 

 Radio Relay League and the Bureau of Standards, it was observ^ed 



