62 J. R. Bakyns — On the Drift of Derbyshire and Yorkshire. 



IV. — On some Points connected with the Drift of Derbyshire 



AND Yorkshire. 



By J, E. Dakyns, Esq., 



H. M. Geological Survey of England and Wales. 



IN a paper of mine on " The Glacial Phenomena of the Yorkshire 

 Uplands," read before the Geological Society of London in the 

 spring of 1872/ I compared the valley of the Wye in Derbyshire to 

 those of the Aire and Calder in Yorkshire. This was a mistake : 

 the Wye rises on the west side of the geological axis and crosses the 

 anticlinal ; but its valley does not cross the physical axis, which is 

 nowhere broken through, as in the cases of the Aire and Calder. 

 The lowest part of the watershed at the head of the Wye basin is at 

 Doveholes, near Chapel-en-le-Frith. I made some observations by 

 aneroid to ascertain the height of this point. The watershed south 

 of Doveholes was by aneroid 1300 feet above the sea, and that north 

 of Doveholes 1250 feet ; but as the glass was falling on the day of 

 my visit, these heights are too great by somewhat less than 75 feet, 

 the total amount of the fall. This will make them between 1225 and 

 1300, and between 1175 and 1250 feet respectively. On another 

 occasion I estimated the height of the watershed north of Doveholes 

 at 1200 feet, and that on the Peak Forest Eailway at 1175 feet. A 

 couple of miles to the N.N.E. I found Sparrow Pit to be 1350 feet 

 above the sea, and Perry dale 1200 ; the plateau above Perry dale 

 1350; the watershed under Mam Tor 1500 ; and the lowest point of 

 Eushup Edge 1525 feet above the sea. 



We may say then that the lowest part of the watershed north of 

 Buxton is about 1200 feet above the sea. 



The general mass of the Drift on the western side of the Pennine 

 table-land reaches to the height of about 800 feet above the sea, 

 though erratics are found at higher levels. In the Memoir of the 

 Geological Survey on Sheets 81 N.E. and S.E., Mr. Green states 

 that the depression of the land in glacial times exceeded 1200 feet. 

 It cannot, however, have been much more than this, as no Drift has 

 found its way over from the Etherow into the basin of the Don by 

 way of Saltersbrook, where the height of the watershed is 1366 feet. 

 Nothwithstanding this, and the total absence of Drift from the 

 plateau of the Wye basin, where not even a solitary erratic is to be 

 seen, I see no better explanation of the occurrence of Drift with 

 foreign stones in the Wye valley than that given by Mr. Green in 

 the S-iemoir alluded to above. 



In the same paper I stated that, with the exception of some 

 Silurian erratics near Threshfield, no foreign ones are found in 

 Wharfedale. At that time I sup^^osed these Silurians to be sur- 

 face erratics, distinct from and subsequent in date to the general 

 mass of Drift ; but I afterwards found them imbedded in the regular 

 Drift. The most northerly point at which they occur is near the 

 Wharfe, a mile and a half above Threshfield : this is where the 

 valley opens out on the west and merges into the Drift-covered plain 



1 See Quart. Journ Geol. Soc, 1872, toI. xxviii., p, 382. 



