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 
womine ePan ‘VARIATION OF SIGNALS = after sunrise at Clif- 
ae AT CLIFDEN den. The received 
FROM MAY 1910 +o APRIL 1917 energy then steadily 
CURVE FOR FIRST DAY OF f 
u decreases again until 
EACH MONTH BEING SHEWN 
DATE yoy 2Ge2len. cauenge i’ Teaches a very 
tn ectickenge>” marked minimum, a 
: f= short time beforesun- 
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 “aes 1911, the vertical dotted lines representing sunset 
and sunrise at Glace Bey 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 (pl. 1, fig. 1). 
Fia. 9. Fia. 10. 
