1848.] SHARPE ON SLATY CLEAVAGE. 123 



Starting from the anticlinal axis north of Skiddaw, the elevation of 

 the beds has gradually diminished as they are farther from the axis, 

 from an angle of 45° to one of 25° ; a result which agrees with the 

 ordinary pheeuomena of elevation, which diminish in amount in pro- 

 portion to the distance from the elevating power. But the angle of 

 inclination of the cleavage-planes has increased as they recede from 

 the axis from 45° to 90°, being lowest at the axis, and perpendicular 

 exactly on the line where the elevating force ceases to act, or is 

 neutralized by meeting an opposing force proceeding from another 

 axis of elevation. This is so precisely analogous to the two cases de- 

 scribed in my former paper as occurring in North Wales and Devon- 

 shire (pp. 90 and 94), as to make it probable that wherever the beds 

 throughout a large area are elevated from a single axis, the cleavage 

 will be found to be arranged in an arch over that axis, with an in- 

 crease of elevation from the axis to the boundary of the area of eleva- 

 tion, on which line we may expect to find it perpendicular. 



On the northern side of the area, the Skiddaw slate is only visible 

 for a breadth of one or two miles on the north of the igneous axis of 

 Carrock Fell ; beyond that distance, both that and all the rest of the 

 older formations are covered up by an overlap of the mountain lime- 

 stone, which is nearly horizontal, and rests unconformably on the 

 Skiddaw slate, which dips N. 25° W. 40°, being a dark brown clay- 

 slate without chiastolite ; the cleavage dips N. 25° W. 30°, being less 

 inclined than the bedding, which is rare in the north of England, 

 though of common occurrence in Cornwall and Devonshire. 



From the momitain limestone of Uldale and Hesket Newmarket 

 covering up and concealing the older formations to the northward, 

 we are prevented from seeing the rest of that side of the area of eleva- 

 tion ; but enough is visible to show us that the Carrock Fell sienite 

 is the axis of the elevation both of the beds and of the cleavage of the 

 area. 



Southern area of elevation. — The Sections 3 and 4 are drawn 

 along the same line through the middle of the southern portion of the 

 slate district of the Lakes, and are arranged on the same principle as 

 the former sections ; No. 3 showing the position of the strata, and 

 No. 4 the dip of the cleavage-planes. They commence on the north 

 of Helvellyn at the porphyry of Greenside, which is on the line of 

 separation between the two areas of elevation of the district, and 

 extend southward to Bowness, beyond which place the cleavage is 

 more faint, and only to be traced at intervals with some difficulty. 

 These two sections are not exactly in continuation of the former, 

 Nos. 1 and 2 ; but, together with them, complete a section across the 

 Lake Mountains. There are however, on the east and west of the line 

 of sections, two small districts where the Skiddaw slate has been raised 

 to the surface by the eruptions of the granites of Booth and Shap 

 Fell, which are not described in this paper*. 



The district traversed by these sections presents in its complicated 

 and disturbed features a most striking contrast to the regularity of 



* For the elevation of the slates of Black Comb by the Booth Granite, see Sedg- 

 wick, Journ. Geo). Soc. vol. ii. p. 111. 



VOL. V. PART I. K 



