94 



HYDROGRAPHY. 



[Sect. III. 



with the sea, when a communication has been or may be 

 made and a scouring power obtained by the admission of 

 the tide through the port. However, what has been said 

 of river basins may be applied to these enclosed sheets of 



water. The principal points are, their distance from the 

 port, height above mean v/ater line of the ocean, depth. 





ensions, and fluctuation of surface, the quality, tem- 

 perature, and sweetness of the water, the nature of the 



bed and borders^ inland navigation. 



if any^ &c. 



-r' 



Artificial Harbours. 



34. In all harbours, but especially in the vicinity of those 

 which are formed by piers carried out into deep water, it 

 is proper to notice whether tliere are shoals formed about 

 the piers, and the pier-heads especially. If there are, 

 obtain information as to the probable cause, when they 



Vr'ere first noticed, carefully note their extent and direc- 

 tion, and connect with them the direction of the tide, ebb 

 and flood, and if there be any stream through the piers 

 out, or in, note its rate, direction, and the distance it ex- 

 form and construction of artificial harbours, 



tends. 



rpi 



piers, and breakwaters, does not properly belong to hyJro- 



biit it may be well to describe and record 

 the form of the breakwater, the pitch or slope of the 

 stonework, the depth in which it is erected, the material 

 of which it is composed, the nature of the work, and how 

 it has resisted th. sea. Or if there be an opportunity of 

 seeing it in a gale of wind, the power any peculiar form 



coaatruction of breakwater may have in repelling a 

 heavy sea, or the eifect «ny peculiar form of pier may 

 have in diverting the sea at the entrance from the 



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 effect- 

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35. 



vessels 



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 vessels 

 time, 



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