1854.] 



SORBY ON YEDMANDALE. 



331 



valley of the Derwent, a portion of which is seen at g, and the bottom 

 of which is from 200 to 300 feet lower than that of Yedmandale. 



Fig. 6 is a section in the line of the centre of the upper part of the 

 valley, the letters on it corresponding to those on the plan, fig. 1 ; and 



Fig. 2. Sect. 1. 



Fig. 3. 

 Sect. 2. 



Fig. 4. 

 Sect. 3. 



Kg. 5. 

 Sect, 4. 



Fig. 6. 



^nW 



^■Itl 



Loiiiritudinal section. 



the dotted line shows the original level of the surface previous to ex- 

 cavation. At ^ e is the steep upper part of the valley of the Derwent ; 

 from e io d the inclination is small, but greater than the dip of the 

 beds ; at c? is the above-mentioned absolute depression, the north side 

 being higher than the south ; from 6? to c is the flat bottom of the 

 higher valley, coinciding with the plane of bedding ; and from c to 

 b is the slope of the centre of the top of the lower ; at the bottom of 

 which, at h, is the deltoid accumulation of detritus. 



Though there are numerous remains of ancient military works in 

 the vicinity, yet the peculiarities I have described are so connected 

 together, and of such a kind as cannot be other than natural. 



Throughout the whole of this upper eastern branch of the valley 

 there is no trace whatever of any brook-course. Why this is so, can 

 easily be understood. The level of the valley of the DerAvent being so 

 much lower ; there being so small a tract to drain ; the dip of the rocks 

 also having a tendency to carry the water into the ravines in which 

 there are brooks, as previously described ; and the coarse nature of the 

 detritus at the bottom of the valley, easily account for there being no 

 stream of modern drainage in it. As mentioned above, the consider- 

 able streams which do enter the valley soon disappear amongst the 

 detritus, and, therefore, one cannot be surprised that the small quan- 

 tity of water tliat must enter this branch of it should disappear. 



