AND OTHER WATER WAVES 91 



height must be of the same order of magnitude 

 as that of the breaking waves of storms. 



On December 29, 1898, in N. 47, W. 19, waves 

 45-52 feet high were reported from S.S. St. Simon. 

 In absence of details I have not used these in the 

 above records of height of waves, but I take them 

 here to calculate a maximum length of storm -wave 

 in the Atlantic during the exceptionally wild 

 weather prevailing at the time of my observation 

 at Branksome. We have already seen that when 

 the length of waves is determined in the manner 

 which gives the highest values (viz., by recording 

 speed and period of arrival from on board ship), 

 tnaximum waves of 40 feet are associated in the 

 North Atlantic with lengths not more than 600 

 feet, or fifteen times the height . The corresponding 

 length for a height of 45 feet is 675 feet, and 

 for 52 feet, 780 feet. The latter is a figure prob- 

 ably considerably in excess of the real average 

 wave-length during the storm, for which 600 to 

 700 feet would be a more likely estimate. Never- 

 theless, if we took the excessive value of 780 feet 

 for the average length of the storm -waves, this 

 would be less than one-half the average length of 

 the swell observed at a distance. 



On February i, 1899, I recorded at the same 

 place a swell of even longer period. The day 



6 



