1848.] SHARPE ON SLATY CLEAVAGE. 127 



The Wenlock flags rest conformably on the Coniston beds, and end 

 with a black slaty flagstone, quarried on the north side of Bowness, 

 which is the equivalent of the Ireleth slate of North Lancashire. 

 There are several anticlinal and spiclinal axes in this scries, and the 

 beds are frequently repeated on the surface, but on the whole the 

 formation dips about S.S.E. The cleavage meets in an axis on Ap- 

 plethwaite Common, and then dips S. 45° E, 85°. It is perpendi- 

 cular on the line of one of the faults, and then dips N. 35° W. 85° ; 

 the dip continues in the same direction as far as Bowness, the incli- 

 nation diminishing from 85° to 70°. 



In the series of coarse greywackes south of Bowness, the cleavage 

 is less marked, and there is sometimes a danger of confounding it 

 with some of the numerous joints which traverse the rocks : for this 

 reason I carried my observations no farther in that direction, al- 

 though I believe that a careful examination of the beds would detect 

 cleavage much farther south. The evidence of the compression of 

 the rock, which is afforded by the distortion of the organic remains 

 in uniform directions, is found in a slight degree through the Upper 

 Ludlow rocks south of Kendal, in beds which hardly show a trace of 

 cleavage ; so that it seems that a slight degree of compression was not 

 sufficient to produce the cleavage. 



If we take a general view of the stratification, overlooking minor 

 disturbances and irregularities, we must regard the great porphyritic 

 bands of Raise and Kirkstone as one great axis of igneous eruption, 

 running nearly east, and elevating the beds into a saddle, those of 

 ndvellyn dipping principally northward, and those south of the axis 

 dipping on the whole southward. But on taking a similar general 

 view of the cleavage, we find no approach to any arch like that seen 

 in the northern area of elevation ; nor even to any regularity of posi- 

 tion. From Helvellyn to Bowness the cleavage (with some few ex- 

 ceptions) dips at high angles to the N.N.W. ; the extreme variation 

 lying between N. 25° W. GH'', and S. 45° E. 85°. Thus it seems that 

 the eruption or the presence of the bands of porphyry has interfered 

 materially wdth the arrangement of the planes of cleavage. 



On comparing closely the relative positions of the bedding and 

 cleavage, it will be seen that there is a fault or axis in the stratifica- 

 tion wherever the planes of cleavage are pei-pendicular, and this co- 

 incidence occurs too often to be due to accident. This is in harmony 

 with the views stated in my former paper, that the direction of the 

 planes of cleavage depended on the direction of the pressure on the 

 beds which accompanied their elevation, and that the cleavage was 

 perpendicular where that pressure ceased to act, or was arrested by 

 another force meeting it in a contrary direction ; for in a district 

 traversed by so many bands of eruptive rocks, the compressing forces 

 which accompanied the elevation of the various masses of rock may 

 have acted independently between each of the erupted masses, and 

 these forces must have neutralized one another where they met at a 

 fault, on which the cleavage is perpendicular. 



Or if it should appear that the cleavage was formed during an ele- 

 vation of the beds at a later period than the eruption of the porphy- 



