ALLUVIAL COVERING. 43 



of the current of the rivers in that quarter, having their tops toward 

 the north-east. This suggests the idea, that the Romans not only 

 filled up stagnant pools with the wood which they cut down, but 

 threw quantities of trees into the rivers, which being carried down by 

 the cuiTents were lodged in abundance upon the adjacent banks. 



Following this idea a little further, may we not conjecture, that 

 the obstruction of the mouth of the Humber might be caused by an 

 accumulation of this floating wood, which lodging in the mud would 

 become a nucleus or basis for new islets or shoals. These mud banks^ 

 being held together, and in some degree consolidated, by the timber, 

 might for some ages be a barrier at the mouth of the river, both im- 

 peding the influx of the tide, and the cun-ent of the fresh water. In 

 that case, the river stemmed by this new bar, behoved to rise higher, 

 so as to flow over it ; and this rise of the river would inundate all the 

 flat country along its course, covering the plains far and wide, where 

 the woods had lately been cut down, and where some remains of the 

 ancient forests were still left. Hence the waters, stagnating in low 

 places over the felled trees, and other vegetable substances, would 

 in the course of some years convert them into peat bog; and the win- 

 ter floods would deposit, over this boggy stratum, successive layers of 

 mud, sand, and gravel, forming a soil adapted for vegetation.* The 

 obstructions at the mouth of the river being gradually removed, after 

 the lapse of several years, the waters would retire from the lands 

 which they had inundated, leaving extensive tracts of soft spongy 

 grounds, covering the ancient surface, and even the peat bogs, to the 

 depth of several feet; while large meres and marshes would still 



* Several curious observations on the formation of peat moss in the bottoms of Jakes ajid on 

 the banks of rivers, and of meadow land over.the peat, may be seen in the first Volume of De 

 Luc's Geological Travels. We might have noticed, when speaking of the termination sea or 

 sey, that see is the usual term for lake in the north of Germanyj of which numerous instance* 

 occur in De Luc's Map. 



