Length, and Velocity of Ocean Waves. 267 



Length and velocity were measured from deck under the 

 following conditions : — Ship, length 380 feet ; speed, 14 knots; 

 course to E. ; sea from W., and therefore right aft. 



Time of crest, 

 running length. 



Time between 

 two crests. 



Velocity. 

 Calculated. 



Length. 

 Calculated. 



12-5 



14-25 



35-5 



445 



12-5 



165 



35-5 



485 



80 



160 



47-5 



765 



This was the heaviest sea we encountered during the whole 

 voyage. The wind was blowing a hard gale from S.W., with 

 squalls of hail and sleet. The sea was certainly high, but did 

 not appear excessively so to the eye. The ship broached to 

 and lay in the trough of the sea for nearly half an hour while 

 a gland in the engine-room was being packed ; but no harm 

 was done beyond splitting a topsail. The ship rolled tremen- 

 dously, but no seas swept over her. 



Under these circumstances the height of 46 feet, given by 

 one set of observations, seems excessive. The actual vertical 

 lift of the cabin was undoubtedly 40 feet ; for, as I noticed it 

 at the time, there is not a mistake in the records. Any error 

 in the true height must come from the estimate of 6 feet for 

 the difference of the height of the eye on the crest and in the 

 trough. 



It will be noticed that the relation of length and velocity 

 to height is very irregular ; but this is due to the character 

 of the waves, and not to errors of observation. On all the 

 days the waves were running irregularly. We never saw 

 crests nearly a mile long chasing one another with a well- 

 defined trough between them ; but the seas were so confused, 

 that sometimes after one big crest nothing followed but some 

 small waves. There was nothing to call a cross sea ; but 

 there were many series of waves of different lengths running 

 pretty much in the same direction, which were constantly 

 interfering with one another. An eye estimate of height is 

 always delusive, but I was surprised that the waves measured 

 as much as they did. I have seen a heavier sea in the Atlantic; 

 so that if we take only 40 feet as the highest of this series, it 

 is perfectly certain that much greater heights are sometimes 

 attained. 



Fitzroy says that, even during many years spent at sea ; a 



