26 



The lowest beds of the slate in High Borrowdale are calcareous, 

 and may perhaps represent the Blawith limestone, which has not 

 been found in conjunction with the slate eastward of Blawith. 



In High Furness, the district of Lancashire consisting of Lower 

 Silurian rocks, the principal valleys run from south-west to north- 

 east, parallel to the strike of the beds, each ridge of hills repre- 

 senting the outcrop of a particular bed : this is not the case with 

 the same formation in Westmoreland, where the valleys of Coniston 

 Water, Esthwaite, Windermere, Troutbuk, Kentmere, Long Sled- 

 dale, Bannisdale, High Borrowdale, and Brethesdale, all follow great 

 faults across the strike of the stratification : these faults are con- 

 tinued through the Windermere rocks, and sometimes into the Lower 

 Ludlow rocks, but are lost before entering the Upper Ludlows. 



It is in High Furness that the Lower Silurian formation is best ex- 

 posed to observation, and has a greater thickness than in Westmore- 

 land, the beds gradually diminishing in their course eastward. In 

 the same district of Lancashire the slaty character of the rocks is 

 more developed than we find it in Westmoreland ; it is especially 

 between Coniston, Old Mere and Kirkby Ireleth, that the crystal- 

 lizing agency which has changed the rocks into slate has acted most 

 powerfully, many beds in that district supplying good slate, which 

 will hardly split up at all elsewhere. 



From the prevailing parallelism long known to exist between the 

 planes of slaty cleavage over considerable areas, Mr. Sharpe considers 

 it nearly certain that these planes had a uniform direction in each 

 district, and that the cases of exceptions which are found are due to 

 disturbing forces acting after the cessation of the cleavage action. 

 In the district under consideration the mean dip of the cleavage 

 planes is considered to be S.S.E. 70°, and the cleavage action is 

 thought to have ceased before the formation of the Upper Ludlow 

 rocks. 



Windermere Rocks. — The beds formerly classed by the author as 

 the lowest division of this series are now placed in the Lower Silurian 

 formation, and the middle and upper divisions are thrown together, 

 for want of any distinct line of division between them, and some 

 considerable corrections are made in their geographical boundaries. 

 They rise, near Ulverston, from below the mountain limestone of 

 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 



