126 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 



The strength of the received waves remains as a rule steady during 

 daytime. 



Shortly after sunset at Clifden they become gradually weaker, and 

 about two hours later they are at their weakest. They then begin to 

 strengthen again, and reach a very high maximum at about the time 

 of sunset at Glace Bay. 



They then gradually return to about normal strength, but through 

 the night they are very variable. Shortly before sunrise at Clifden 

 the signals commence to strengthen steadily, and reach another high 



maximum shortly 

 "WJUATION OP SIGNALS 

 AT CLIFDEN 



FROM MAY 1910 to APRIL 1911 

 curve: for first day of 



EACH MONTH BEING 

 DATE 



V»l«l»TH)N.SICII*t» 



ci.imtN 



WRING APRIL 11)11 





SHEWN 



5UNRI5C VfrtlM} 



■ MOON '■■'«"• SW«8« curocN (^»r 



mti , ' 'V ' nVftA^'^V '7 -' 



iuf«ci *)«it 



MAYl 



after sunrise at Clif- 

 den. The received 

 energy then steadily 

 decreases again until 

 it reaches a very 

 marked mhihnum, a 

 short time before sun- 

 rise at Glace Bay. 

 After that the signals 

 gradually come back 

 to normal day 

 strength. 



It can be noticed 

 that, although the 

 shorter wave gives on 

 the average weaker 

 signals, its maximum 

 and minimum varia- 

 tions of strength very 

 sensibly exceed that 

 of the longer waves. 

 Figure 9 shows the 

 variations at Clifden 

 during periods of 24 

 hours, commencing at 

 12 noon throughout 



the month of April, 1911, the vertical dotted lines representing sunset 



and sunrise at Glace Bay and Clifden. 



Figure 10 shows the curve for the first day of each month for one 



year, from May, 1910, to April, 1911. 



I carried out a series of tests over longer distances than had ever 



been previously attempted, in September and October of last year, 



between the stations of Clifden and Glace Bay, and a receiving station 



placed on the Italian Steamship Principessa Mafalda, in the course of 



a voyage from Italy to Argentina (pi. 1, fig. 1). 





Fig. 9. 



Fig. 10. 



