57 



The springs which the excavation opened in the rock bed were 

 highly charged with proto-Carbonate of Iron, no doubt produced 

 by the decomposition of Iron pyrites. 



It is not, however, so much the Liassic formation which gives 

 an interest to the section as the recent deposits of gravel and 

 peat, disclosing as they do, the results of the operation of 

 natural laws in the river valleys of the district. 



The gravel deposit is distinct from, and more recent than, the 

 more extensive beds, which, commencing at Stroud and con- 

 tinuing through Cainscross and Stonehouse, run far into the 

 vale in the direction of the Severn. It is, in fact, the ancient 

 bed of the Frome, while the older beds are at a higher level, 

 and were once the drifts and shores of a lake, which nearly, if 

 not quite, covered the surface of the vale of the Severn. This 

 may, perhaps, be considered a rather large assumption, but it is 

 probable there was a time when such a lake existed, and the 

 streams of the Stroud valleys formed one or more irdets of it for 

 the following reasons: — 1st. The height of the older gravels 

 above the sea — namely, 160 feet, clearly proves the existence of 

 a body of water at that elevation. 2nd. The appearance of the 

 cliffs and the bed of the Severn at Aust, indicate the probable 

 existence, at some former period, of high land across the present 

 bed of the Severn sufficient to retain the waters, and so form an 

 extensive lake, covering the vale to the height of the gravel beds 

 at Stroud and other locaHties, of which the gravel beds were the 

 beaches ; and, 3rd., because all the organic remains hitherto 

 found in these gravels pertain either to the land or fresh water. 



If such a lake existed, the high land at Aust would, by the 

 action of the outfall current passing over it, be gradually 

 denuded, a channel would be formed, and gradually deepened, 

 until, eventually, the lake would be drained. The streams from 

 the hills would then, on their way to the Severn, commence the 

 excavation of new and deeper channels, the smaller valleys which 

 now intersect the district would be formed, and new gravel beds, 

 such as the one under consideration, would be deposited, the 

 gravel being probably derived from the washings of the slopes 

 of the more ancient deposits. 



