where the means are resorted to, or otherwise afforded ; 

 and such is the case with that of the Po, the Mile, and 

 many other places in similar situations. 



As soon, almost, as a city is founded, at the entrance 

 of a river into a bay or gulf, the inhabitants, in order 

 to favour their commercial views, commence the ope- 

 ration of w barfing, dyking, &c. as occasion may re- 

 quire. If a part of the city happen to be on each side 

 of the river, a corresponding course is pursued, and 

 the river is not only confined to a less breadth, but is 

 goon extended into the bay or guli, beyond its usual 

 limits. The bed of the river, having no longer a de- 

 scent, and the waters of the bay or gulf retaining the 

 same height and level, the current of the river is 

 checked ; the small quantity of alluvion that may have 

 been suspended in its current above, is deposited ; the 

 offals and washing of the streets of a city by rains, be- 

 ing thrown into the river, are likewise deposited, and 

 greatly increase the quantity. 



In a few years, as dyking and wharfing are ex- 

 tended, the evil is found to increase ; for the wrters of 

 the river, having a still greater distance to pass be- 

 yond the original limits of the bay, where the river 

 formerly discharged itself, are still more retarded, and 

 only the lighter particles of alluvion are suffered to 

 pass off into the bay or ocean. In this state of things, 

 while the sources of alluvion are constantly augment- 

 ing, in proportion to the increase of population, and 

 the cultivation of the lands in the vicinity, the naviga- 

 tion of the river is found to be obstructed, from the ele- 



36 



