508 



BELL SYSTEM TECHNICAL JOURNAL 



the interval between the time of incidence of the sun's rays at the 

 position assumed for the damping region and actual sunrise is some- 

 what less than at the northern observation points. However, a 

 seasonal effect may be responsible as is indicated by the dotted curve 

 in Fig. 6. 



32 

 30 

 28 

 26 

 24 

 u 22 



lao 



a. 



CD 16 



2 



3:30 



4:00 4:30 5:00 



NEWFOUNDLAND STANDARD TIME-AM 



5:30 



Fig. 7 — Rate of occurrence of tweeks. Data taken during a period of high intensity. 



There is a distinct seasonal variation in tweek numbers, the rate 

 being consistently high during the summer and low during the winter 

 and early spring — following approximately the variations in non- 

 musical atmospherics. x'\t times in the summer, tweeks have been 



