OBSERVED OFF THE CAPE OF GOOD HOPE. 435 



the Beaufort scale^ and many of the crests being above 20 

 feet in height,, I availed myself, in latitude 33° 38' S., lon- 

 gitude 15° o' E., of the opportunities thus afforded of 

 making some further observations on waves. 



When a ship is running before the wind, the order of 

 succession of the waves cannot be so well observed as when 

 she is hove to; no sets were therefore taken. On the 

 other hand, the speed of the waves and the breadths of the 

 troughs are better observed when running ; and to these 

 points I devoted myself. 



With waves of 1 6 feet in height, and breadth of trough 

 300 to 350 feet, the ship running 10 knots, I estimated the 

 following times occupied by the waves in passing along the 

 ship's length (200 feet) :— 4'^ 5'^ 5", 6", 6", 6", f, f, 

 and 8". With troughs of 250 feet, the ship^s speed being 

 10 knots, I obtained for the times of passage 6", 8", and 8''. 

 These numbers will give the following speeds of the waves 

 in nautical miles per hour: — 37, 29, 29, 25, 25, 25, 22, 22, 

 and 18, and 25, 18, and 18. The highest waves observed 

 this morning were 18 feet; and their length, measured along 

 their bases, varied from 400 to 500 feet. 



The wind slightly increased during the morning. I ob- 

 tained, when its force according to the Beaufort scale was 

 marked 7-8, the times of passage 6" and 6", giving the 

 speeds of the waves 25 nautical miles per hour. Their 

 estimated lengths at this time were from 400 to 500 feet, 

 the widths of the troughs varying from 200 to 350 feet, the 

 ship's speed remaining the same. 



In the afternoon (the force of the wind marked 7), the 

 widths of the troughs being 250 to 300 feet, and certainly 

 not exceeding the latter estimation, I obtained for times 

 of passage 5" and 6", giving speeds of 29 and 25 nautical 

 miles per hour. 



Although some of the discrepancies exhibited by the 

 foregoing estimations evidently arise from errors of estima- 



