AND OTHER WATER WAVES 129 



strong breeze verging on a moderate gale i.e., 

 a wind velocity of about 28 statute miles per hour. 

 At 3 p.m. there occurred a squall lasting 3 minutes, 

 which converted a moderate to a large sea. I esti- 

 mated that the height of the waves increased ,at 

 least 2 feet per minute, finally attaining rather 

 more than 20 feet. Not only did the waves 

 increase in height, but the crests lengthened out 

 transversely, so that the waves ran in longer and 

 more regular ridges. The squall came from the 

 starboard and abaft. Two minutes after it had 

 passed us we were among waves no larger than 

 before, but I could see a group of about four 

 great ridges travelling away with the squall. The 

 length of the waves, as judged by their appearance 

 in relation to the ship's length, was never more 

 than 200 feet. As has been already explained, 

 this estimate is generally less than the measure- 

 ments obtained by following the waves in their 

 course . 



In another squall, occurring at 5.2 p.m. and 

 lasting 5 minutes, the height of the waves was 

 perceptibly increased. 



Next day, December 24th, we were in 

 N. Lat. 33 3$', W. Long. 43 58'. The princi- 

 pal " waves " were mounds of water, produced by 

 the crossing of two sets of waves. At 3.30 p.m. 



