84 HARBOUR CONSTRUCTION. 



permanent way rails (Vignole's section) upon the piers, although 

 cramped to the blocks, were torn off; and in some cases, where 

 the cramps could not be wrenched out or broken, the rail itself 

 was torn away from them, leaving behind the piece of rail 

 flange which was held by the cramp. 



At the Manora breakwater, during one monsoon, seven 20-ton 

 concrete blocks, which had been placed on the roadway of the 

 breakwater for the purpose of sheltering the " Titan," were dis- 

 placed, four of them being upset, and the remaining three made 

 to skid some feet by the stroke of the sea. The roadway of this 

 breakwater was, however, exceptionally low, being only about 

 2 feet above high water of spring tides. 1 



At Wick, during one storm, two stones, one weighing 8 tons 

 and the other 10 tons, were thrown over the parapet of the 

 breakwater, the top of which was 21 feet above high water. 



Enormous blocks of concrete, weighing respectively 1350 tons 

 and 2GOO tons, were also displaced there ; but, from a personal 

 inspection of the work, and from descriptions given to me by 

 those who were engaged upon it during construction, I believe 

 that the displacement of these masses was in a great measure 

 due to the failure of the foundations. It would, therefore, 

 probably not be correct to attribute their disturbance entirely to 

 wave-stroke, heavy as it undoubtedly must have been. 



In reference to the above, Mr. Parkes said 



" I would direct attention to the exceptional character of this 

 case, and to the impossibility of ascertaining all the conditions which 

 might have contributed to so extraordinary a result. Had this been 

 simply the largest instance on record, standing at the head of a 

 series of cases approaching to it by gradations, I would have been 

 more disposed to draw general conclusions from the fact. But it 

 seems to stand alone. To argne from it would be to condemn as 

 dangerous every sea-barrier in existence, and to contradict the most 

 trustworthy results of experience." 2 



At Alderney, stones of 9 tons' weight were lifted by the force 

 of the waves from the foreshore, or seaward slope of the mound, 

 and thrown over the top of the wall, a height from where they 

 originally rested of 45 feet. 3 



At the Dhu Heartach lighthouse, off the west coast of 



1 The surface of this breakwater is now below high water, owing to settlement 

 having taken place. 



8 Min. Proc. Inst. C.E., vol. xliii. p. 52. 3 Ibid., vol. xxxvii. p. 90. 



