HYDROGRAPHICAL SURVEY. — WAVES. 223 



indicating the prevalence of storms in the imme- 

 diate neighbourhood, without ever being reached 

 by the storms by which such swells are produced. 

 Thus, in latitude 68°, in the month of July 1813, 

 I experienced heavy swells from the E. N. E. and 

 W. S. W., distinctly visible at the same time, while 

 the wind was from the south. In latitude 63°, in 

 April 1815, we had strong swells from both the 

 northward and southward, indicating storms on 

 both sides of us, while we had light variable winds ; 

 and before these subsided, an additional swell from 

 the eastward made its appearance ; occasionally the 

 three distinct swells might be observed at the same 

 time, but most generally only one of them was very 

 conspicuous. In the month of July 1816, while 

 crossing the North Sea, swells from the N. E., S. W. 

 and E. occurred together ; and in April 1817, 

 heavy distinct swells from the W., N. W. and 

 S. S. E., prevailed at the same time. 



Swells in the polar seas are often the harbingers 

 of storms. They are more considerable near the 

 edge of firm ice, or among loose drift-ice, than in 

 the open sea. And in the same way waves are often 

 higher near shore and in shallow water than in the 

 Main Sea. In the Greenland Sea, intermitting 

 swells are not uncommon, especially among ice. I 

 call them intermitting, because several waves of re- 

 markable magnitude appear in succession, and then, 

 for an interval of perhaps some minutes, the swell is 

 almost imperceptible. 



