118 WAVES OF THE SEA 



than the height of the swells observed on 

 February ist. 



The charts throw a clearer light upon the swell 

 observed at Branksome Chine on February ist. 

 This had a period of 22.5 seconds, and therefore 

 a speed in deep water of 78.5 statute miles per 

 hour. A group of these swells travelling freely 

 for a long distance under the action of gravity 

 advances at 39.25 statute miles per hour. Now, 

 the charts for the days January 29th to Febru- 

 ary ist show Beaufort's 11-12 (64-77 statute miles 

 per hour) only on January 3Oth, and the positions 

 of the arrows showing force 9-10 on 3 ist and ist 

 are too distant to affect the water at Branksome 

 Chine on ist. The cyclonic system of Janu- 

 ary 3Oth half-way between North America and 

 England is a very deep isolated depression, with 

 wind of force 11-12 in N. 45, W. 41, the direc- 

 tion of this wind being a little S. of W. This 

 wind, and that a little in advance of the black 

 arrow, would send a swell almost directly to the 

 entrance of the English Channel. The distance 

 of the straight run from N. 45, W. 41, to Cape 

 La Hogue (which I shall take as the distance to 

 Branksome Chine) is 28, 1,680 geographical 

 miles, 1,960 statute miles. The difference of time 

 between local noon January 3oth in W. 41 and 



