WAVES OF THE ATLANTIC AND GERMAN OCEANS. 27 



I shall now contrast the indications of the Marine Dynamometer by stating a 

 few facts regarding the ascertained effect of the waves in the elevation of spray, and 

 in the transportation of heavy masses of rock. This is more especially important, 

 as to some, the results indicated by the instrument have appeared greater than 

 they could have expected ; and it has even been supposed that, were they correct, 

 the stones which constitute our marine works would be scattered. Before passing 

 from this point, it may be well to observe that the stones composing sea- works, 

 are not only wedged and compacted together, but they derive from the superin- 

 cumbent courses, (independently of the support afforded by the backing), a pressure 

 so great as to cause an amount of friction Avhich is in most cases greatly more 

 than sufficient to preserve them in their places. 



But to return to the facts of the ascertained effects of the waves, it may be 

 interesting, in the first instance, to give some idea of what may be looked for in 

 comparatively small expanses of water, such, for instance, as the lakes of North 

 America, which, however, exhibit during gales of wind, all the characteristics of 

 an open sea. In the north-eastern corner of Lake Erie, the harbour of Buffalo was 

 constructed at a cost of about L.40,000. It is mentioned in the " Civil-Engineering 

 of North America," that the author " measured (at this harbour) several stones 

 which had been moved ; and one of the largest of them, weighing upwards of half- 

 a-ton, had been completel}^ turned over, and lay with its bed or lower side upper- 

 most." 



In the Firth of Forth, at the Granton Pier works, on 19th December 1836, 

 after a gale from the north-east, one stone was moved measm-ing fifteen cubic 

 feet, or about one ton in weight, and thrown on the beach, after having been built 

 into the wall ; and a stone containing 18 cubic feet was moved 30 feet from 

 its place ; while the pierres perdues or mound-stones were washed down to a slope 

 of about 4 to 1. 



The folloAving instance, which occurred at the landing slip of the Calf Point, 

 Isle of Man, affords a proof of the great force of the waves even in the Irish Sea. 

 During a gale from the north-west, a block was lifted from its place in the wall 

 and thrown landwards, which measured 123^ cubic feet, equal to about 10 tons 

 weight. 



In the German Ocean, we can refer to the BeU Rock Lighthouse,* which, 

 though 112 feet in height, is literally buried in foam and spray to the very top, 

 during ground swells, when there is no wind. It is, therefore, a very important 

 station for making such experiments, because the rise of the spray may be 

 regarded as a scale by which the results of the Marine Dynamometer can be 

 checked or compared. 



* At such a situation as the Bell Rock, a column of water or of air could be conducted into the 

 interior of the house, and might, in the one case, shew the force of each wave as it struck the building 

 by the rise of the water column ; or, in the other, by a pressure-gauge, shew the same resiilt in atmo- 

 spheres by compression. 



