218 



KENNIE'S DOCKS AND HARBOURS. 



PART VII. 



at great cost, are found comparatively inaccessible in 

 severe weather, is, we believe, to be accounted for 

 mainly by the circumstance that they have been laid 

 out after no definite rule or principle whatever. If they 

 succeed, it is often the result of a happy accident ; and 

 if they prove failures, it is supposed that it could not 

 have been helped. Even within the last twenty years 

 several expensive havens have been constructed, which 

 have proved to be so dangerous that they can scarcely 

 be used. But by Mr. Eennie's forms of piers, vessels, 

 if they have only steerage-way, must enter the har- 

 bour in safety. They cannot strike on the pier-heads, 

 if the most ordinary care be used, the very recoil 

 of the waves forcing them forward into port ; and, 

 as any swell which might enter would have ample 

 space to expend itself, the ship could either be brought 

 up, or take the beach without damage if necessary. 

 Again, a sailing vessel, on leaving the harbour, sup- 

 posing the wind to be blowing right in, could lie out 

 upon either tack and make an offing, if it were prudent 

 to put to sea at all. And although the narrowed distance 

 between the two pier-heads might be termed the entrance, 



an angle of 120 degrees with it, so 

 that both the outer arms made simi- 

 lar, kants with each other. A large 

 space would thus be enclosed, which, 

 he believed, would make a very com- 

 modious and capacious harbour. " By 

 the above construction," he says in 

 his report, " though it may seem that 

 its exposure will admit of the swells 

 from the south and south-west getting 

 into the harbour, yet when it is con- 

 sidered that the angle at which a 

 wave will strike the Heads will occa- 

 sion a rebound in a similar angle to 

 that in which it is struck, and as this 

 will be the case from each Head, it 

 follows that these reflected waves, 

 meeting each other, will occasion a 

 resistance which will have the effect 

 of preventing a considerable part of 

 the sea-wave from entering the har- 

 bour, and what does enter it will ex- 



pend its fury on the flat beach within 

 and soon become quiet." This might, 

 he added, be in a great measure pre- 

 vented by extending the pier-heads 

 further seaward, but which the large 

 additional expense precluded him 

 from recommending ; and, indeed, 

 there would always be abundant shel- 

 ter for the shipping under one or 

 other of the pier-heads. Besides, as 

 the Frith was only about two miles 

 wide at the place, the probability 

 was that there would be no such 

 heavy seas as to render so ex- 

 pensive a measure necessary. The 

 plan was, however, carried out to 

 only a limited extent, and we merely 

 quote the report for the valuable 

 principles to be observed in the con- 

 struction of harbours, which are here 

 so clearly enunciated. 



