198 Correspondence — Mr, George Maw, 



late Professor Baden Powell, suggests my recording one or two facts 

 relating to the disposition of the Red marls on the older rocks that I 

 noticed when visiting the district with the British Association excur- 

 sion in August, 1866. 



Professor Powell observes, " that there are several localities where 

 the New Eed has undergone some disturbance since its deposition," 

 and gives an engraving of the Swithland Slate Quarry in illustration, 

 which does not, however, seem to support this view. In all the 

 sections I examined, the dip appeared wholly independent of disturb- 

 ance, and due to an irregular base line of deposit, an element which 

 is often overlooked in estimating the extent of changes of inclination 

 subsequent to deposition. The Red marls of Charnwood Forest dip 

 away in every direction from the high ground of the older rocks 

 towards the surrounding level plain ; but I was much struck with 

 the fact that the direction and amount of inclination seemed to be 

 less related to the entire mass of the high ground than to its details 

 of contour. In the section of Swithland Old Pit, given at page 119, 

 the two masses of Red marls are represented dipping towards a gully 

 intersecting the slate. A subsequent movement of the slate is not, 

 however, required to account for this, and an examination of the beds 

 m situ conclusively show that the details of inclination are directly 

 related to the original surface -contour of the fundamental rock, a 

 point which is faithfully represented in diagram No. 2 of Professor 

 Jukes' memoir.^ A similar arrangement is observable in a cutting 

 of the Bristol and Exeter Railway near the Bourton Station,- where 

 the Keuper beds rise and fall at considerable angles of inclination 

 over some prominent bosses of Carboniferous Limestone, and had not 

 the fundamental rock been visible, the sudden changes of dip might 

 appear to have been the result of disturbance. 



Another noticeable feature in Charnwood Forest is the relation of 

 the areal outline of the Red marls to the surface contour of the older 

 rocks rising above them ; long winding tongues of the red beds run- 

 ning up into the ancient valleys of the high ground, the contour of 

 the exposed portions of which is entirely in harmony with that of 

 the bottoms of the valleys buried beneath the remnants of the later 

 deposit. This affords a good illustration of the extreme antiquity 

 of the surface contour and hill-and-valley system of the Palaeozoic 

 rocks; and whatever form of erosion may have determined this 

 contour, it has evidently been very little modified by marine erosion 

 during the submergences of the Trias and succeeding formations. 

 In fact, the general surface contour of the high ground, and all the 

 principal hills and valleys of Charnwood Forest were in existence 

 before the period of the Trias, for remnants of the Red marls occupy 

 the ancient lines of waterflow, and these do not appear to have been 

 changed by subsequent disturbances. 



George Maw. 



Benthall Hall, Broseley, March 6th, 1868. 



' In Potter's History and Antiquities of Charnwood Forest. 



2 See Section, Fig. 2, page 443, Geological Magazine, Vol. III., October, 1866. 



