HEIGHT 



21 



sible to determine the effective fetch with some accuracy, also led to the 

 conclusion that the waves caused by ordinary winter gales averaged 

 about 1.5 times as high (in feet) as the square root of the fetch (in 

 nautical miles) for distances up to 300 to 400 miles (Stevenson, 1874, 

 pp. 23-26). And the heights derived by this formula, which has been 

 accepted in many of the more recent discussions, correspond fairly well 

 with the heights of waves that have been measured elsewhere in storms 

 or ordinary intensity. Waves, for example, 22 to 23 feet high have 

 been recorded in the Duluth Canal on Lake Superior, where the fetch 

 is 259 nautical miles (Gaillard, 1904, p. 69), as compared with 24.1 

 feet, according to the formula ; and a 30-mile wind has been observed 

 to produce 22-foot waves in the western Meriterranean. where the fetch 

 from the windward shore was about 260 nautical miles, i. e., where 

 24-foot waves might be expected (Cornish, 1910, pp. 36-40). It is 

 obvious, however, that since this formula takes no account of the 

 strength of the wind, it cannot be invoked indiscriminately, else serious 

 errors will result. Thus a 20-mile wind, which should produce a 

 7.5-foot wave with a fetch of 25 miles according to the formula, and 

 one of 15 feet with a fetch of 100 miles, would actually produce waves 

 of only about 6 feet and of 8 feet, respectively, at these distances. 



The average heights of waves. — The accounts of the early voyagers 

 of the last part of the eighteenth century and of the first quarter of the 

 nineteenth contain many reports of mountainous waves — especially in 

 the stormy Southern Ocean. But it has long been known that their 

 reports were greatly exaggerated. While waves up to 40 to 50 feet 

 high, or even higher, do occur, as described below (p. 23) , during severe 

 and prolonged gales, the common run of waves are very much smaller, 

 even in the most tempestuous regions (See table 8.). 



Table 8. — Relative frequency of waves of different heights in different regions 

 [Adapted from a chart, based on 40,164 extracts from sailing ships' log books, in Schumacher, 1939] 



Region 



North Atlantic, between Newfoundland 

 and England 



Mid-equatorial Atlantic 



South Atlantic, latitude of southern 

 Argentina _ 



North Pacific, latitude of Oregon and 

 south of Alaskan Peninsula 



East equatorial Pacific _. 



West Wind Belt of South Pacific, latitude 

 of southern Chile. 



North Indian Ocean, Northeast monsdon 

 season 



North Indian Ocean, Southwest monsoon 

 season 



Southern Indian Ocean between Mada- 

 gascar and northern Australia 



West Wind Belt of southern Indian Ocean 

 on route between Cape of Good Hope 

 and southern Australia 



Height of waves in feet 



0-3 



Percent 

 20 

 20 



3-1 



Percent 

 20 

 30 



20 



20 

 35 



20 



25 



15 



25 



Percent 

 20 

 25 



20 



20 

 25 



20 



10 



25 



20 



20 



7-12 



Percent 

 15 

 15 



20 



15 

 10 



20 



5 



20 



15 



20 



12-20 >20 



Percent 

 10 

 5 



Percent 



