FOR GREAT BRITAIN AND IRELAND. 47 



safe passage of vessels. Both extremities of all single 

 isolated breakwaters are, of course, free ends, as are also 

 the seaward ends of all single breakwaters which are 

 connected with the land." 



4th. " Straight piers (Fig I, d, facing p. 80). A straight 

 pier generally projects, at right angles, to the coast-line, with 

 a free end at its seaward extremity, and, unless when the 

 wind blows right in upon the shore, will always afford some 

 shelter on its lee-side. In order to get the full advantage 

 of this kind of pier, both sides are sometimes finished as 

 quay walls, and the parapet, if there be one, is built in the 

 middle of the roadway." 



5th. " Quay or wJiarf (Fig I, e, facing p. 80). A quay 

 wall is usually built parallel^ to the line of the shore. It 

 affords no shelter of any kind, and the only advantage 

 which it possesses is that of enabling vessels to load and 

 unload without their having to beach, or where the shores 

 are steep, even to take the ground." 



" The same object may also be effected by an open 

 framework of timber piles by a suspension bridge, with 

 a wharf at its outer end or by a floating pier, rising 

 and falling with the tide, and connected with the shore by 

 a bridge." 



"It will be observed that all the kinds of piers or harbours 

 just enumerated differ materially from each other in the 

 amount of shelter which they afford, and are therefore 

 suitable for places having very different degrees of exposure. 

 In some places there are shores which lie open to the full 

 fury of the ocean, while other parts of the same coast are 

 protected in some directions by projecting headlands or 

 islands. Then, leaving the main coast, we have the shores 

 and bays of narrow sounds, whose breadths vary at 

 different places ; and, lastly, we have creeks so perfectly 



