5 4 2 Post-glacial A lluvia. 



historical times, as, for example, in the case of the 

 alluvial meadows of the Ouse, once a commodious 

 estuary, in which the Saxon fleets could ride as far up 

 as Alport, a mile above Lewes. Further north the peats 

 and broad marshy alluvia of the Wash lie on Boulder- 

 clay, and the same is the case with what may be called 

 the recent warps of the Humber and much of the 

 loamy alluvial strata that cover the broad plain of 

 York and pass northward to the Tees, between the 

 Oolitic escarpment and the uprising of the western 

 slopes of the Magnesian Limestone and Carboniferous 

 rocks. The gravels and clayey alluvia of the Wear and 

 the Tyne play the same part, beautiful examples of the 

 latter being well seen on the banks of the Tyne below 

 Newcastle, and above that town at the junction of the 

 North Tyne with the larger river. In great part of 

 the Severn valley the same kind of phenomena are 

 apparent, and indeed in many of the river valleys of 

 England the occurrence of old river detritus above the 

 Boulder-clay is not to be doubted. 



These gravels and other alluvia were therefore often 

 made by rain and the wasting action of the rivers 

 sometimes working on the Boulder-clays, and some- 

 times partly wearing out new valleys, and when flooded 

 spreading sediments abroad on their banks. As in the 

 older alluvia, so in these more recent deposits, it is 

 natural that many bones of Mammalia should be found, 

 a few of which may be of extinct species. It is, how- 

 ever, certain, that in the subject of river-gravel 

 Mammalia, there has been a good deal of confusion 

 arising from the habit of their having been assumed to 

 be all of the same age. 



I have already stated (p. 482) that after the deposi- 

 tion of the Glacial deposits, Britain, by a considerable 



