224 HARBOUR CONSTRUCTION. 



Sometimes especially in small fishery harbours piers are 

 made to terminate with a semicircular or square end only the 

 width of the pier, additional strength being given either by 

 adopting a better class of masonry, by dovetailing or dowelling 

 the blocks together, or in some other way. Piers terminating 

 in this manner are in some ways more convenient than those 

 with hooks or projections, inasmuch as they afford greater 

 facilities for small vessels or fishing-boats working along them, 

 and so getting away to sea. In some situations, however, this 

 convenience may be more than counterbalanced by the run of 

 waves along the pier, which often proves very troublesome. 



This wheeling of waves around pier-heads, and the range 

 which it causes along the harbour side of piers, is not, as a rule, 

 sufficiently realized in designing works, and it not infrequently 

 happens that it has to be dealt with later on. 



Lights, for the guidance of vessels entering harbours at 

 night, are usually exhibited from pier-heads. This necessitates 

 the erection of small lighthouses, for which room should be 

 provided when designing the heads. Dioptric lights of the 

 fourth or fifth order are suitable for this purpose ; but for small 

 fishery harbours sixth - order lights will generally be found 

 sufficient. 



A pier-head is also usually furnished with a capstan for 

 the arms of which a clear sweep of from 12 to 15 feet radius is 

 required and with mooring-posts, fairleads, etc. 



