25 



as Mr. Sharpe considers erroneously : nevertheless, although no 

 fossils have been found in them, he considers them to be the upper- 

 most bed of the Lower Silurian series, because they are always con- 

 formable to the undoubted Lower Silurian beds below them, and are 

 not equally conformable to the bedsabove. As this southern edge forms 

 the boundary line of the Lower Silurian formation, Mr. Sharpe traced 

 them carefully along their whole course, from their first appearance 

 rising from under the mountain limestone, on the east of Ireleth, till 

 they are hidden by the old red sandstone of Birkbeck-beck. Near 

 Ireleth it is only used for building- stone, but at Kirkby Ireleth are 

 quarries extending for a mile and a half along the range of the bed, 

 supplying dark-blue slates of very good quality. At Horse Spital 

 Quarry the beds dip south-east 80°, and the cleavage dips south-east 

 55°, both sets of planes striking north-east : this coincidence in the 

 strike of the bedding and cleavage planes is common in all this 

 district ; yet at Lord Quarry, close to the last-mentioned, the beds 

 dip N.N.E. 20°, while the cleavage dips S.S.E. 70°. Further east 

 the rock is of inferior quality, and is rarely worked for roofing-slate: 

 its usual course is north-east, passing by Suberthwaite, Blawith, 

 Nibthwaite, at the foot of Coniston Water, where much building- 

 stone has been quarried, and the rock is well exposed, being a dark- 

 blue flagstone streaked with gray : between Oxen Park and Satter- 

 thwaite it dips north 50°, and N.N.W. 70°, and is lighter and more 

 striped than usual ; at Force Mill it strikes E.N.E. and dips N.N.W. 

 65°, and the cleavage has the same strike but is perpendicular : at 

 Satterthwaite the dip is north 45° : between Esthwaite and the 

 Ferry on Windermere the road runs near the upper edge of the bed, 

 which is well exposed close to the Ferry House, north of which spot 

 it reaches more than a mile up the shore of the lake. On the east 

 side of the lake it has been quarried north of Bowness. 



Eastward of Bowness, Mr. Sharpe corrects an error which he 

 committed in laying down this line too far south : he now traces it 

 nearly E.N.E. by Ing's ChapeJ, Row Gill, and Hugill Hall, dip 

 south-east 60° ; Monument Hill on the Avest side of Kentmere, dip 

 S.S.E. 80° to Fellfoot in Kentmere. The flagstone crosses Long 

 Sleddale at the Chapel, where it M'as found not worth working for 

 slate : at Bonnisdale-head Farm it gives a slate of fair quality, the 

 beds dip south-east by south 65°, and the cleavage dips in the same 

 direction 80° ; from here it crosses into High Borrowdale half a mile 

 above High House, dipping south-east by south 50° ; a fault down 

 this valley throws the bed below High House on the east side of the 

 valley : in the next Fells it is much concealed by the vegetation, 

 but it is seen at a cutting of the road from Shaj) to Kendal on Hurd's 

 Brow, between the ninth and tenth mile-stone, dipping south-east 

 75°, and the cleavage dipping north-west 85°. Near the Borrow 

 the beds are thrown into several anticlinal ridges bearing north-east, 

 by faults which disturb the cleavage planes as well as the bedding 

 of the rock : this slate has also been worked in the upper part of 

 Bretherdale. The boundary thus laid down nearly corresponds with 

 that given in the new edition of Mr. Greenough's map. 



