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



land, both by day and night. The change from day to night con- 

 ditions is much more abrupt at sea than on land. Stray storms us- 

 ually accompany convective weather. 



On October 5, 1920, severe strays were observ^ed by receiving stations 

 in New England, and no New England short-wave transmitting sta- 

 tions were heard outside of that locality. Transmission elsewhere 

 was excellent. 



Direction of signals. (Variation with time, wave-length, distance 

 and kind of wave.) — Changes in the direction of the wave front of 

 waves reaching a receiving station from a given transmitting station 

 are observed only at long wave-lengths, but are especially marked 

 with continuous waves. They are far more noticeable at night than 

 in the daytime. On 15,000 meters enormous changes in direction 

 are observed at night (as much as 90 degrees within half an hour), 

 while the changes observed during the daytime are very small, seldom 

 exceeding ten degrees. On 1000 meters, direction changes as great 

 as ten degrees are seldom observed. 



The readings of direction can seldom be made sharply while changes 

 in direction are occurring. Sometimes when it has been changing 

 very rapidly it becomes impossible to determine on any direction, 

 the direction-finder giving no indication of a minimum signal in any 

 position. The minima observable are less distinct at night than 

 during the day. All direction changes are greater at night than in 

 the daytime. 



Direction changes are very small at very short distances from the 

 transmitting station, are great at medium distances, and small again 

 at very great distances from the transmitting station. These facts 

 have been observ^ed particularly regarding signals from the New 

 Brunswick, New Jersey, radio station. 



Eckersley states the belief that waves are refracted in passing from 

 sea to land and vice versa. Tests of radio compass stations indicate 

 that those stations which receive signals entirely over water have 

 no error. 



Effects of sunrise and sunset. (Intensity, fading, strays, and di- 

 rection. Variation with wave-length.) — Great variations in the 

 intensity of radio signals of all wave-lengths, even up to 15,000 meters, 

 are observed at sunrise and sunset. Such variations are especially 

 noticeable when transmission is in an east and west direction. 



Transmission is not as good between stations when the boundary 

 between dark and daylight intervenes as at other times of the day. 



