226 ME. H. H. ARNOLD-BEMEOSE ON THE GEOLOGY OF [May 1899, 



(4) Bentley Hall. 



The fourth cutting, opposite Bentley Hall, abont 690 yards lonj?, 

 is in a tough Boulder Clay which contains many well-polished and 

 grooved limestone-boulders. At the end nearer Tissington the Clay 

 rests upon shales. Immediately north of the cutting, in an old 

 quarry near the point where the railway crosses the Buxton road, is 

 an exposure of shales and limestones dipping in an easterly direction. 

 The limestones are black in the interior, but covered by a weathered 

 crust, which gives them the appearance of sandstone : they contain 

 bands of chert in which foraminifera occur. 



(5) Waslibrook. 



The fifth cutting, east of Washbrook Cottage, about 290 yards 

 long, is in Boulder Clay at either end, underneath which shales and 

 thin limestones are seen for a short distance in the centre. 



The railway now makes a curve to the east, and describes nearly a 

 semicircle round the eastern part of the village of Tissington. After 

 leaving the cutting in Boulder Clay, it crosses a small valley in the 

 soft ash, and enters the sixth cutting. 



In the three cuttings to which the remainder of this paper is 

 devoted, four exposures of thick ash may be seen, each overlain by 

 shales and limestones, with intercalations of tuff. Por the sake of 

 distinction only, and not implying thereby any diiference in compo- 

 sition, the term ash will be restricted to these four exposures, while 

 the thinner intercalations of volcanic detritus will be called tuffs. 



(6) Tissington. (Pis. XYII & XYIII.) 



This cutting is about 1060 yards long, and may be naturally 

 divided into three nearly equal portions — the northern, central, and 

 southern. A bed of ash about 144 feet thick, below which is seen 

 a few feet of cherty limestone on the eastern bank of the cutting, 

 occupies the whole of the central portion, and dips beneath the 

 contorted shales and limestones in the two other parts of the cutting. 

 The cherty limestones below the ash are now only visible on the 

 eastern side, where they are bent into an anticline : they were 

 formerly to be seen across the railway. During the excavation they 

 were seen dipping at an angle of 40° across the cutting, and thus only 

 2 feet of the uppermost beds appeared at the bottom of the eastern 

 bank under the ash, which dipped with and overlay them. After 

 a short time they were hidden by debris. The line at this point 

 passes through a dome, composed either of the upper cherty beds 

 of the Mountain Limestone, or of the basement-beds of the Yoredale 

 Series. The ash is exposed for a much greater distance north of the 

 dome than south of it, and there are indications that this part of the 

 volcanic deposit has been bent into a long syncline and anticline 

 before it dips under the shales in the northern portion of the cutting. 



