s. A. adamson: the skipton and ilkley railway. 207 



continue thus vertical to the west side of the quarry, and, indeed, 

 Tiear the summit of the section in one spot were noticed even to 

 turn over a Httle upon themselves, thus actually reversing the order 

 of deposition. The dark-coloured limestone was seen to be traversed 

 by innumerable veins of calcite, which were noticed, generally speak- 

 ing, to be approximately transverse to the surface of the beds. An 

 •embankment was now passed over about a quarter of a mile in length, 

 on which will be situated the Bolton Bridge Station, distant from the 

 Devonshire Arms about three-quarters of a mile. The cutting No. 9 

 was then entered, about 400 yards in length. The greatest depth 

 ■of it is 31 feet, and here we arrive at the next division of the Car- 

 boniferous formation — the Yoredale rocks. These consist largely of 

 black shales, but contain also beds of earthy and sandy limestones 

 ■and sandstones. In this particular cutting the beds observed were 

 black shales (dipping to the S.E. at an angle of 25 degrees), and a 

 little further on were noted some beds of black limestone, which had 

 thus been stained by decomposed organic matter, most probably fish 

 remains, for, on breaking pieces off, a peculiar fetid smell was felt, 

 somewhat resembling that from petroleum. The dip soon caused 

 these strata to disappear, their place being taken by a drab-coloured 

 fine-grained gritstone, full of detached specks of mica. This was 

 evidently a good and valuable stone, as it had been used for 

 bridges, etc. We then emerged upon an embankment about 350 

 yards in length, and this point was an excellent vantage ground for 

 ^ fine view of the heather-clad and lofty grit summit of Beamsley 

 Beacon, also of the beautiful valley of the Wharfe and Bolton Woods. 

 Another cutting about 300 yards long will at this point have to be 

 made for the further progress of the line, but is not yet commenced. 

 We now arrived at the deep, well-wooded ravine of Lob Gill, cut 

 through the Yoredale shales by the action of a small rivulet. Here 

 and there the shales were exposed, weathering into their original 

 state of clayey mud. The ravine will eventually be crossed by a 

 viaduct of five arches, at a height of 70 feet above the bed of the 

 stream. The cutting No. loa was now traversed, about 300 yards in 

 length, with a maximum depth of 26 feet. The black shales were 

 here observed to be slickensided. Layer after layer was detached, 

 all presenting the same fine glossy polish. The movement of the 

 mass must therefore have been general. Slickensides are often 

 found traversing beds in the neighbourhood of a fault, but in this 

 case the beds of shale having a sharp dip, this effect would probably 

 be produced by the beds of shale slipping upon each other. 

 Another short embankment, about 200 yards in length, was then 

 crossed to cutting No. 11, about 250 yards in length, with a maximum 



July 1887. 



