and their Action on Floating Bodies. 85 



like a vast fly-wheel, the acquired momentum of the air. 

 Assuming the great forces which set the atmosphere in 

 motion to be derived from heat, we may conceive the sun to 

 be the prime source of power, and the ocean probably as tlie 

 mightiest reservoir of its force upon earth. There is no 

 cessation of its giant activity, and it may without error be 

 said, that from the time an ocean vessel leaves one port to 

 the time she enters the next, she is lieaving upon perpetual 

 waves. 



12. To instance the force thus a^CTreffated in waves, there 

 is mentioned that at Port Sonachan in Loch Awe, with the 

 diminutive fetch of only 13 or 14 miles, a stone weighing 

 \ ton was torn out of the masonry of the landing slip, and 

 overturned by a wave (Enc. Brit. Art. Harbors, 8th ed.), 

 and a stone | ton weight was similarly moved and over- 

 turned at Buffalo (Stevenson's Engineering of North 

 America). At Barrahead, one of the Hebrides, a wave was 

 seen to strike a block of granite of 50 tons weight, and 

 move it several feet. In November, 1817, the waves of the 

 German Ocean, where the fetch is 600 miles, overturned, 

 just after it had been finished, a column of freestone 36 feet 

 high, 17 feet base, and at the point of fracture 11 feet in 

 diameter {Enc. Brit. Art. Lighthouses). The prodigious 

 impulse requisite to do this is shown in the height to which 

 waves ascend against cliffs and headlands. Such effects are 

 witnessed in their utmost grandeur in the islands on the 

 west coast of Scotland, on the sides of icebergs, and at many 

 points on the South African and Australian shores. So also 

 at lighthouses ; at Bell Rock and Skerryvore, waves are 

 known to dash completely over the summit of the 

 edifices ; and a magnificent spectacle is presented at Cape 

 Northumberland in South Australia, where a massive rock, 

 said to be from 70 to 100 feet in height, is swept by every 

 sea durino' a sjale of wind. 



13. In the German Ocean, with a fetch of 600 miles, the 

 height of waves varies from 13 to 20 feet : the Mediterranean 

 with the same fetch, gives the same results. But these 

 proportions sink into insignificance in comparison with the 

 great mid-ocean waves of the Atlantic and South Pacific. 

 I)r. Scoresby (Brit. Assoc, 1850) states, the maximum 

 height of waves off the Cape of Good Hope to be 43 feet : 

 other writers make it considerably more, and it has even 

 been estimated that, from summit to summit of tliese 

 enormous masses of water, a distance of nearly the fourth 



