414 



ILLUSTRATIONS OF tHi 



advanced part into the fea, in proportion to the 

 fupply from behind. 



The conftant agitation of the waters, and the 

 declivity of the bottom, are no doubt the caufes 

 of this gradual and widely- extended depofition. 

 A foft mafs of alluvial depofite, having its pores 

 filled with water, and being fubjedl to the vi- 

 brations of a fuperincumbent fluid, will yield 

 to the preiTure of that fluid on the fide of the 

 leaft refifl:ance, that is, on the fide toward the 

 fea, and thus will be gradually extended more 

 and more over the bottom. This will happen 

 not only to the finer parts of the detritus, but 

 even to the grofl"er, fuch as fand and gravel. For 

 fuppofe that a body of gravel refl:s on a plane 

 fomewhat inclined, at the fame time that it is 

 covered with water to a confiderable depth, that 

 water being fubjed not only to moderate re- 

 ciprocations, but 



al ib 



fuch 



g 



fee occafionally communicated to the 



f 



ocean ; the gr 



ligh 



by 



being rendered 



merfion in the water, and 



that account more moveable, will, when the un- 

 dulations are confiderable, be alternately heaved 

 up and let down again. Now, at each time that 

 it is heaved up, however fmall the fpace may 

 be, it mufl: be fomewhat accelerated in its de- 

 fcent, and will hardly fettle on the fame point 



where it refl:ed before. Thus it will gain a lit- 

 tle 



