1865.] BRITISH ASSOCIATION. 355 



has been eaten out by the agency of that river, the more so when 

 the deep fissure is at once accounted for when we see the abrupt 

 severance that has taken place between the rocks which occupy its 

 opposite sides. In that part of Shropshire, the Severn has not 

 worn away the rocks during the historic era, nor has it produced a 

 deeper channel; whilst in its lower parts it has only deposited silt 

 and mud, and increased the extent of land on its banks. 



Then, if we turn to the district in which we were last assembled , 

 the valley at Bath is known to be the seat of one of those distur- 

 bances to which my eminent friend Sir Charles Lyell candidly 

 applied the term " convulsion" ; the hot waters of that city having 

 ever since flowed out of a deep-seated fissure, clearly marked by 

 the strata on the one side of the valley having been upheaved to a 

 height very different from that which they once occupied in con- 

 nexion with those of the other side. When, indeed, we look to 

 the lazy-flowing, mud-collecting Avon, which at Bath passes along 

 that line of valley, how clearly do we see that it never scooped out 

 its channel ; still more, when we follow it to Bristol, and observe 

 it passing through the deep gorge of Mountain-limestone at Clifton, 

 every one must then be convinced that it never could have produ- 

 ced such an excavation. In fact, we know that, from the earliest 

 periods of history, it has only accumulated mud, and has never 

 worn away any portion of the hard rock. 



From such data I conclude that we cannot apply to flat regions, 

 in which water has no abrading power, the same influence which 

 it exerts in mountainous countries ; whilst we are also compelled 

 to admit that the convulsive dislocations of former periods produ- 

 ced many of those gorges in which our present streams flow. To 

 pass, indeed, from the environs of Bath and Bristol, and even from 

 the less distant Coalbrook Dale, you have only to contemplate the 

 tract which lies between Birmingham and Dudley, and endeavor 

 to satisfy the mind as to the process by which it has been planed 

 down before the surface was covered by the Northern Drift ; for 

 the great dislocations which this tract has undergone, as proved by 

 many subterraneous workings, must have left a highly irregular 

 surface, which was so levelled by some very active causes as to 

 obliterate the superficial irregularities corresponding with the 

 interior disturbances. In short, what was this great power of 

 denudation which took place in a tract where there are no moun- 

 tains whence powerful streams descended, and in which there are 

 no traces of fluviatile action ? Must we not, in candor, admit 



