ALLUVIAL COVIERING. 41 



of the Huraber. It is certain, that the mouths of large rivers are 

 subject to great variations, being sometimes qiiite open, and some- 

 times greatly obstructed by the formation of sand banks or mud 

 islands. Such shoals have existed, and still in some degree exist, at 

 the mouth of the Humber; and we may easily believe, that at the dis- 

 tance of some ages, the mouth of this river was so choaked up, as to 

 allow only a very partial flow of the tide, and occasion a large ac- 

 cumulation of fresh water on all the flat lands through which this river 

 and the streams that feed it hold their course. An obstniction of this 

 kind would necessarily produce large meres and marshes, throughout 

 the woody plains of Deira and of Lindisey. 



But here a question arises, which indeed might have been started 

 sooner, How came the bottoms of these meres or lakes to be so re- 

 plenished with decayed trees, and other vegetable matter, as to acquire 

 the nature of peat bogs? To this we answer, that various causes may 

 be assigned for this fact. Even in the ordinary course of nature, 

 wherever there are fresh water lakes situated in woods, a deposition 

 of vegetable matter will gradually take place in the bottoms oi the 

 l,akes, from the annual fall of leaves and decay of plants and shrubs, 

 and the occasional fall of withered branches and tininks of trees. 

 This natural process of decay will, in the lapse of some ages, yield a 

 thick stratum of vegetable matter, as may be seen in the woods of 

 America. But it is evident, that the hand of man has greatly accele- 

 rated the accumulation of this matter, in the bottoms of our lakes or 

 meres. Some think, that our ancestors, in clearing out the land for 

 the purposes of agriculture, threw the trees into lakes and ponds and 

 hollow places, as the easiest way of getting rid of them; wood bein^- 

 with them of no more value, than it is now in the back settlements of 

 America. This is Dr. Plot's opinion. The fact under consideration, 

 however, is far more likely to have resulted from the arts of war, 

 than from those of peace. It is well known, from the testimony of 



