288 HARBOUR CONSTRUCTION. 



work, or of useful deductions being drawn therefrom, such should 

 be carefully noted. 



The relative strength and duration of the flood, ebb, or other 

 littoral currents, considered in relation to the wave-action on 

 the shore, will indicate the preponderance of scouring power in 

 one direction or the other, and so the probable direction of drift ; 

 but every effort should be made to substantiate, or otherwise, 

 any theory based upon such observations by others of a more 

 direct nature. 



For such purpose small coal, pieces of burnt clay, or other 

 easily recognizable material, may be deposited at points along 

 the coast in various depths of water, and its movement be noted, 

 it being remembered that the direction of drift may vary with 

 the weather or season. 



