1 86 A TEXTBOOK OF OCEANOGRAPHY 



from the land plays an important part. Atmospheric pressure 

 is also of importance. The relation of wind to current at the 

 exit of the Baltic is seen from the following table, which is 

 the result of 5,918 observations at the Gjedser Riff Lightship 

 off Falster Island. 



WIND AND CURRENT AT GJEDSER RIFF. 



Even with a westerly wind the outgoing current (i.e., 

 against the wind) predominates; the outgoing current is still 

 more remarkable during calms. As to the yearly periodicity, 

 the outgoing stream is most frequent in spring, when it con- 

 stitutes 76 per cent, of the observations, this, of course, being 

 the period when the fresh water from the land is at its 

 maximum and the prevailing winds are from the east. In 

 summer the frequency sinks to 60*5 per cent. ; at this time 

 westerly winds are common. In autumn the percentage is 71 

 and in winter 69. The currents are at times very strong. In 

 the Belt they attain a velocity of 3 to 4 miles an hour. The 

 average at Gjedser is o'i5 knot. 



Along the south-east coast of Sweden the current runs 

 south, and thence out through the Sound, Cattegat, and 

 Skager-Rack. On the German coast the current has an 

 easterly trend. 



In the Gulf of Finland in calm weather the current is 

 westerly, and is composed of water of low salinity. It is a 

 feeble current and runs more to the north or Finnish side of 

 the Gulf. Bottom currents of salter water run in the reverse 

 direction, so that the waters of the Gulf are never quite fresh. 

 The surface salinity is lowest at the commencement of July 

 and highest in w r inter, when storms stir up the water. Bottom 



