300 Proceedings of the British Association for 1850. 



rose above the visible horizon, — ^hence they must, like those 

 of the preceding day, have been 30 feet waves. But one 

 important difference should be noted, — viz., that they were of 

 no great extent on the ridge, presenting, though more than 

 mere conical peaks, but a moderate elongation. Another 

 subject of consideration and investigation, on this occasion, 

 was the period of the regular waves overtaking the ship, and 

 the determination, proximately, of the actual width or inter- 

 vals, and their velocity. 1. The ship was then going nine 

 knots only, the free action of the engines being greatly in- 

 terfered with by the heavy sea running, and the lines of 

 direction of the waves and the ship's course differed about 

 22^ degrees, the sea being two points on the larboard quar- 

 ter, — in other words, the true course of the ship was east; 

 the direction /rom whence the sea came was WNW. 2. The 

 period of regular waves, in incidental series, overtaking the 

 ship were observed as follows : — 



3. The length of the ship was stated to be 220 feet. The 

 time taken by a regular wave to pass from stern to stem ap- 

 peared, on a mean of several observations, to be about six 

 seconds. Hence 6" : 220 feet (the width passed over in that 

 time) : : 16" 5 feet to 605 feet (the width passed over betwixt 

 crest and crest.) But this extent, by reason of the obliquity 

 of the direction of the waves to the course of the ship, is 

 found to be elongated about 45 feet, reducing the probable 

 mean distance of the waves to 559 feet. Independently of 

 this process, I had previously estimated the distance of the 

 wave crests, ahead and astern when the ship v/as in the hol- 

 low, as 1 stood near the centre of the ship's length on the 

 paddle-box, at 300 feet each way, by comparing the intervals 

 betwixt my position and the place of the wave-crest with the 

 known length of the ship. This comparison frequently re- 



