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carefully studied than those further seaward in deep water, which allow a 

 wider margin for contingencies. By constructing jjiers in comparatively 

 shallow water, and within the tidal range, we form abrupt projections from 

 the general outline of the shore ; the effect of thus interfering with the 

 tidal or littoral currents is always problematical, and if they are 

 not so governed or modified that the silting tendency of the flood 

 tide is fully counterbalanced by the scour of the ebb, the result may 

 be very prejudicial to the normal condition of the port. 



At the entrance to some harbours, a phenomenon may be observed 

 due to the interception of the tidal and shore currents, and it is sometimes 

 very clearly defined at the entrance to Whitehaven Harbour, (see Plate.) 

 During the ebb, the current setting south from Redness Point is intercept- 

 ed by the outflow from the harbour ; the curve of mutual counteraction 

 of these two opposing forces is frequently defined by a zone on the surface 

 of the water, which attains its maximum convexity towards the sea during 

 the first half of the ebb, when the depth and momentum of outflow is 

 greatest. The convexity of the curve towards the sea, clearly shows that 

 the tendency of the shore current to set into the harbour, is overpowered 

 by the outflow of the ebb. Now if we formed a secondary 

 outlet for the tide so as to diminish the momentum of outflow 

 at this point, the curve of mutual counteraction would then probably 

 become convex towards the harbour instead of towards the sea as 

 at present, thus indicating the set of the shore current into the 

 harbour, carrying with it the sand or other matter held in sus- 

 pension ; deposition would ensue and periodical dredging would be 

 necessary to maintain a navigable fairway. 



Piers to afford shelter from the prevailing storms, such as the West 

 Pier, (see Plate) are generally formed polygonal in plan or constructed in 

 a series of cants, terminating with a bold pier-head. This not only gives 

 the structure increased lateral stability, but, in addition, the cants or 

 elbows change the direction of the waves, and finally the bold pier-head 

 checks the fetch of the sea across the harbour mouth, which might 

 otherwise sweep the vessels to the lee-ward of the entrance. 



