324 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 5, 



laminae of the Devonian (Carboniferous ?) slate very regularly and 

 distinctly bent or curved backwards, or towards the south. The idea 

 of a more powerful agency than rain or frost then seemed to suggest 

 itself ; but it was not until I had examined more extensive sections 

 further to the west, on the east Exmoor hiUs, that I became con- 

 vinced of the necessity of having recourse to a more uniformly 

 efficient cause than even the most exaggerated form of what is com- 

 monly called atmospheric action. The object of this paper, how- 

 ever, is not so much to theorize on the precise nature of this cause, 

 as to state several important facts. 



2. Sections in a Quarry near Wiveliscomhe. — In a quarry about a 

 mile and a half from Wiveliscomhe several very instructive sections 

 of the terminal curving-back of laminae are exposed. The slates 

 (which have a southerly dip) appear to be very flexible ; and this 

 may be partly the reason why they have been so little broken. But 

 the wonderful continuity of the curvature here exhibited must, I 

 think, be partly due to an extreme uniformity in the movement. 

 The bed of curved slates (represented in the figure), on the western 



Sections of curved lamince near Wiveliscomhe. 



N . . S_ 



A. The profile of the laminas. 



B. Their face. 



side of the entrance to the quarry, is from three to four feet thick. 

 The line of demarcation between the commencement of the curving 

 back and the undisturbed mass of slates below is remarkably distinct 

 and straight on looking along the strike of the cleavage; but on 

 looking at nearly right angles to the strike, the surface formed by 

 the edges of the laminae beneath, though equally distinctly marked, 

 is very uneven, as if the once superincumbent moving agent had 

 exerted considerable inequality of pressure, so as to give rise to 

 irregular grooves and ridges. The upper surface of the bed of curved 

 laminae, which is very uniform, is overlain by a layer, nearly two 

 feet thick, of reddish loam, containing fragments of quartz &c. On 

 the opposite side of the entrance to the quarry the curving back for 

 some distance is on a nearly level plane. Here the bed of displaced 

 laminae is from two to three feet thick. It exhibits a double cur- 

 vature, approaching the shape of the letter S. Over it there is a 

 layer of about two feet of loam, with many quartz fragments, chiefly 

 angular, but occasionally a little rounded. 



3. Terminal Curvature of Lamince near Raleigli's Cross. — There 

 are several facts connected with the foregoing sections which ob- 

 viously point to a powerful and uniformly operating cause ; but the 

 belief in such a cause becomes irresistible as one surveys the nume- 



