Silurian Rocks of Westmoreland and North Lancashire. 537 



Low Furness, dipping E.S.E. at high angles, and disappear in West- 

 moreland beyond Bannisdale, during which course they rest on the 

 Kirkby Ireleth slate ; but their southern boundary can only be under- 

 stood from the map, as to the west of Windermere they are over- 

 laid by large patches of mountain limestone, and in their range east- 

 ward are gradually covered up unconformably, and concealed by the 

 Lower Ludlow rocks. In some places the similarity of the rocks of 

 the two formations, and the absence of fossils in both, makes it diffi- 

 cult to determine the boundary between them, the best guide being 

 the dip and strike of the rocks. In Mr. Sharpe's first map a portion 

 of the Lower Ludlow rocks on the north-east of Kendal was errone- 

 ously coloured as belonging to the Windermere series ; the error 

 was pointed out by Cornelius Nicholson, Esq., of Cowan Head, who 

 assisted the author materially in mapping the neighbourhood of his 

 residence. 



The upper boundary of the Windermere rocks begins on the south- 

 west at the lower point of Witherslack, and is marked by a great 

 fault which crosses the valley between that hill and Whitbarrow, 

 and appears to pass under the mountain limestone of Whitbarrow, 

 then runs north-east through Underbarrow, by the Chapel, to Mount- 

 joy : on the west side of this fault the Windermere rocks form high 

 ridges of hard slaty grits of dark grey colour, with lighter streaks, 

 dipping N.N.W., while on the east side of the fault is a gritty rock 

 of uniform grey colour dipping E.S.E., overlaid with beds containing 

 the fossils of the Ludlow beds. From Mountjoy the line turns to 

 the north-west, and passes round Crook Chapel, which stands on a 

 ridge of the Windermere grits ; at Crook Common it turns to the 

 north-east, and follows that direction to near Borrowdale, where the 

 formation is lost, being completely hidden by the Ludlow rocks, 

 which there rest on the Lower Silurians. Crook Common is thrown 

 into great confusion by the meeting of two lines of elevation, one 

 coinciding with the E.N.E. strike of the Lower Silurian rocks, the 

 other coming up from the S.S.W. through Cartmel Fell. 



At Backbarrow, below Newby Bridge, the upper beds of this 

 series are slaty, with a wavy cleavage dipping N.N.E. 80°, the beds 

 dipping south-east 80° ; these beds contain irregular calcareous 

 nodules in great abundance, and Orthoceras articulatum was found 

 in them. 



Mr. Sharpe refers to his former memoir for the description of the 

 Windermere rocks on the east of the Lune, which extend to Grey- 

 rigg Forest, Whin Fell, and Howgill Fell ; in these Fells are several 

 axes of elevation which require further examination. 



Ludlow rocks. — These were described in the author's former paper ; 

 the area covered by them is larger than was there stated, their lower 

 boundaiy being now carried more to the north, and their eastern 

 portion being extended in a sort of trough between the Lower Silu- 

 rian slates of Shap Fell and the Windermere rocks of Whin Fell, 

 crossing Barrowdale between High and Low Barrowbridge. 



In the lowest beds of the series in Fawcett Forest were found 

 Lcptcena lata and Turritella conica, in a slaty rock. The Terebratula 

 navicula is found thinly scattered throughout all the lower part of the 



