THE HUMAN SPECIES. 6? 



when first they became historically known, under the 

 name of Cassiteredes. In the Irish Channel, submer- 

 sions, perhaps even greater than in any other part of 

 England, appear to have occurred, and phenomena on 

 shore are equally surprising. A part of the bed of the 

 Severn is stated to have risen, in 1773, to the height of 

 thirty feet, the back water immediately forming a lake, 

 which was drained by cutting a new channel. Accord- 

 ing to Camden, and Bishop Hakewill's Apology, at the 

 time of the Norman Conquest, part of Pembroke form- 

 ed a promontory, extending towards Ireland ; but the 

 space was already sunken beneath deep sands in the 

 time of Henry II., when a violent storm so far un- 

 covered the original surface, that many stumps of trees 

 appeared fixed in the earth, " and the strokes of the 

 axe upon them quite fresh." 



In the Welsh Triads, Orkney, the Isle of Man, and 

 the Isle of Wight, are styled the three adjacent islands 

 of Britain ; and they proceed to mention the subse- 

 quent separation of Anglesea from the main land. 

 Nennius similarly alludes to the three adjacent islands ; 

 yet, since that period, Orkney became divided into 

 several parts ; and it is evident, that other portions 

 of Wales and Western Scotland likewise became insu- 

 lated. So many important changes, particularly in the 

 British Channel, imply the agency of forces which 

 were not in activity at very remote periods ; for, had 

 they been of primeval date, their operation would have 

 effected the whole of the changes they necessitated long 

 before the dates here mentioned. 



