AND OTHER WATER WAVES 117 



attained 77 statute miles per hour at 10 p.m. on 

 the 27th, and 7 1 statute miles per hour at 2 a.m. on 

 the 28th. Beaufort's 11-12 (i.e., 64-77 statute 

 miles per hour) was recorded at sea in N. 49, W. 

 35, on 28th, and N. 52, W. 19, on 29th. Thus it 

 is proved that the winds that blew had at times 

 an average velocity 10 statute miles per hour 

 greater than that of the swell observed at Brank- 

 some Chine on December 29th. I am not able, 

 however, to derive the observed swell from the 

 hurricane arrows shown on the charts for noon 

 December 28th and 29th, for they are too far 

 off for the swell, if travelling with the group 

 velocity of 34 statute miles per hour, to reach 

 Branksome Chine at the observed time. A feature 

 of the chart for the 29th which is worth noticing is 

 the existence of W. and SW. winds of Beaufort's 

 9-10 (44-53 statute miles per hour) near the 

 entrance to the English Channel. In the moderate 

 depths of the Channel the speed of the swell must 

 have been so reduced ' that the observed velocity 

 of wind on the morning of the 29th was sufficient to 

 exert pressure upon the swells. This may account 

 for their reaching Branksome Chine with a height 

 unusually great for this locality, and much greater 



1 The maximum speed of a wave in 20 fathoms is about 43 

 statute miles per hour. 



