964 



BULLETIN OP THE BUEEAU OF FISHERIES 



Long series of measurements of the currents at various lightships in the Baltic'* 

 have shown the nontidal surface drift averaging about 30° to the right of the wind, 

 and much more often to the right than to the left. Analysis by Forch (1909) of the 

 relationship between the wind in the eastern Mediterranean, and the drifts there, as 

 reported in ships' logs for the Arabian Gulf by Galle (1910), have brought out a 

 corresponding tendency for the current to set about 40 to 60° to the right of the 

 wind.°° According to the current tables published by the United States Coast and 

 Geodetic Survey (1923), local winds off the eastern coast of the United States like- 

 wise produce currents setting about 20° to the right of the wind direction at a veloc- 

 ity about 13^ per cent of that of the wind.'^ 



The Baltic measurements just mentioned had already proved that the current 

 sometimes sets to the left of the wind, due, no doubt, to the effect of the coast 

 line. This relationship between coast line and wind current has been brought out 

 very clearly by a recent investigation of the currents at five lightships along the 

 Pacific coast of the United States by the Coast and Geodetic Survey. For a 

 detailed account of these observations the reader is referred to Marmer (1926 and 

 1926a). In summary they are as follows: Offshore winds and winds parallel to the 

 shore, if having the latter to the left, produce surface currents averaging 20 to 25° to 

 the right of the wind; but if the wind blows against a coast line lying to the right 

 of its track, at an angle of 45° or less (i. e., a southwest wind against a north and 

 south shore line), the current is deflected to the left as it strikes the coast, as might 

 naturally be expected from ordinary observation on the behavior of the tides. 



The observations tabulated below (p. 964) for Portland lightship also show the 

 nontidal current drifting to the right of the wind during months when winds blowing 

 toward the southern half of the compass favor the dominant southerly set. When 

 the wind blows toward the north or northeast against the current, the latter may or 

 may not be reversed. If it is, the resultant set may be either to the right of the 

 wind or slightly to the left of it, depending on the complex interaction between 

 direction and strength of wind, nontidal set, and the trend of the coast line. 



' The directions are those toward which winds and currents set. For full data see pp. 861 and 8C2. 



»' Dinklage (1888), Witting (1909), summarized by Kriimmel, 1911, p. 451. 



»' For theoretic discussion and explanation of modern mathematical methods of calculating wind currents see Ekman (1905), 

 Krummel (1911), Sandstrom (1919), and Smith (1926). 



*8 This statement has as its basis current measurements taken at a large number of localities, some of which are discussed above 

 (p. 963). 



