27 



the Upper Lias, and the Inferior Oolite vdth the Sands, pervious 

 beds resting against impervious, it is easy to perceive how 

 this arrangement must have affected the drainage, and have 

 given direction to the stream. On reference to the Geological 

 Map, (Sheets 34 and 44,) it will be seen in how marked a 

 manner the streams in the Truffham Yalleys follow the hnes of 

 Faulting. In this locality the Fullers Earth Clays, greatly 

 broken by Faults, provide the retentive beds which have formed 

 barriers and conductors to the waters. The Fault on the line of 

 which the lower part of the Truffham Valley has been formed, 

 is intersected by the Sapperton YaUey, which receives and carries 

 westward the waters of the Truffham streamlet. The Fault 

 extends southwards, across an elevated tract, and on its line a 

 streamless valley commences, the drainage of which is into the 

 Bristol Avon. 



In the third place, the present configuration of this district 

 has been brought about by the removal of a large portion of 

 these irregularly deposited and irregularly elevated strata. 



In order to form a just idea of the amount of denudation 

 which has taken place, it is needful to take, in imagination, a 

 bird's-eye-view of the district, and to realize the fact, that all 

 the strata we now see composing the hills were once con- 

 terminous ; they must have been deposited in continuous beds, 

 but are now cut by vaUeys, which, commencing on the higher 

 grounds in slight depressions, rapidly deepen, and in a very 

 short distance attain a depth of more than 400 feet. These 

 valleys are to be seen converging at one or two points, and 

 finally opening out into the vale of the Severn through the 

 western escarpment, with on one side the bold headland of 

 Selsly Hill, rising to the height of 525 feet above the stream ; 

 and on the other side, Randwick Hill, of an equal altitude. 

 Between these two points the beds of the Inferior Oolite, a mile 

 and a half in lateral extent, have been removed, with the 

 exception of a little patch capping Doverow Hill, 



In like manner the beds of Great Oolite have disappeared 

 between Bo^vn Hill and Minchinhampton Common, a distance 

 of more than a mile and a half. The whole amount of rocks. 



