HEIGHT OF WAVES. 



53 



navigator Scoresby made in 1847, lie measured waves from 26 to 

 29 J feet, and tlie average of all his observations gave a height of 

 about 19 feet for the largest waves. On his return in 1848, he found 

 the average to be 30 feet, and some among the waves he measured 

 rose to about 43 feet above the trough of the sea. Other navigators 

 have given similar estimates for the highest crests of waves in the 

 North Atlantic ; but the mean elevation is much less. One can form 

 a good notion by the following diagram, drawn by the engineer 

 Middlemiss to represent the annual variations of the wave at Lybster 

 on the coast of Scotland. 



JbroaryPebgu^Macrch Aprfl May June Jaly An^t Sep^.^Oct^?^ NdV^f^ l)e^^ 



usi S! « I :\ ij 



Fig. 19.— Average heights of Waves observed at Lybster (Scotland) in 1852. 



In the South Atlantic the height of the waves is certainly greater 

 than in the northern parts. Many seamen have seen the water rise 

 to between 50 and 60 feet off the Cape of Good Hope, where the 

 basins of the Atlantic and the Indian Oceans meet. Dumont 

 d'Urville even asserts that he has seen waves above 108 feet high, to 

 the depths of which the ship descended as into a valley, and M. 

 Fleuriot de Langle attests the truth of this assertion. These are in- 

 deed the mountains of which poets sj)eak, and which, in fact, seem 

 such to those who find themselves at their mercy. It is probable, 

 too, that the highest waves of the sea have not yet been measured. 

 One remarkable thing is, that it is not usually during the most 

 violent tempests that the hugest waves are formed. On the contrary, 

 the force of the atmosphere which then precipitates itself obliquely 

 on the waves, so to speak, depresses and crushes them.* 



The waves are developed in all their majesty when the wind is at the 



* Cialdi, Sul moio ondoso del mare, p. 139. 



