the mouths of rivers on the Chesapeak bay, and parti- 

 cularly at the mouth of the Severn ; the current of 

 which, during the heaviest rains, was, perhaps, never 

 sufficiently strong and rapid to float the sand, of which 

 the flat is composed at the entrance of that river, one 

 mile ; and for reasons which it is not necessary to 

 mention here. 



The increase of alluvion from this cause, may be 

 thought to be very small, indeed ; and as bearing no 

 comparison with that brought down by the current of 

 rivers ; but it must be considered, that a recurrence of 

 this cause may happen every week, or continue for a 

 week. Whereas, rivers seldom bring down much al- 

 luvion, except during the heavy autumnal rains, or the 

 melting of the snows in the spring, which rarely occur 

 more than twice in the year. 



Having briefly considered the phenomena of winds, 

 and their operations in increasing the quantity and ex- 

 ten^ion of alluvial formations, I shall proceed tu ex- 

 amine, 3dly, that which is occasioned, either directly 

 or indirectly, by the labours of man. 



That which is caused directly by the labours of man, 

 is by dyking, filling up, &c. and that which is occa- 

 sioned indirectly, is the accumulation of tilth and offals 

 from a city, which, when it is a large and populous 

 one, amounts, in the course of a few hundred years, to 

 an inconceivable quantity. 



These may not be considered strictly as alluvion ; 

 nevertheless, they both constitute powerful auxiliaries 

 in the increase and extension of deltas, or made ground. 



