ON CLEAVAGE AND FOLIATION IN ROCKS. 



381 



which induced Mr. Sharpe to emplojr the terms "anticlinal and synclinal," 

 and to represent the lines of cleavage as parts of elliptical curves*, to which 

 however, they really bear but slight reseu'blance. 



It is further evident, that when the dips of the strata are most uniform in 

 direction, the cleavage also mostly dips in one direction ; and that where the 

 strata are subject to much contortion and frequent changes of dip, the 

 cleavage is either vertical, or deviates only a few degrees (5° to 10°) on either 

 side of the vertical. For the most part the cleavage planes are steeper than 

 the surfaces of the strata. 



The most prevalent direction of the cleavage strike in Westmoreland is 

 E.N.E., varying however to E. and N.E. This corresponds nearly with the 

 strike of the beds. In the country east of Kendal, about Hougill Fells, it is 

 nearly E. and W. (N. 80° E,, N. 85° E.), In the same vicinity the beds strike 

 E.N.E. and N. 85° E., or on the whole a little more to the northward. Pro- 

 ceeding to the S.E., we find cleavage well-developed in the clearly bedded 

 rocks of Ribblesdale, subjacent to the mountain limestone, which shows no 

 sign of cleavage. The beds of slate are marked by graptolites and shells; the 

 cleavage is always traceable. The beds are undulated on axes directed 

 between 15° north of west, and 3° north of west. (In a certain limited roll, 

 the strikes vary 37° (from 22° north of west to 15° south of west). The 

 cleavage strike is nearly parallel, in a general sense, to the strike of the beds ; 

 it varies only 10° (from 16° north of west to 6° north of west).) There is 

 one principal synclinal roll of the strata (b), with dips on the north side (n) 

 of 46° to S.S.W.; on the south side (c) 60°, 73°, 80° to N.N.E. ; then for a 

 narrow space the beds are vertical (d) ; after which is a broad band of dips 

 (e) 76°, 80°, 76°, &c. to N.N.E. 



Fig. 16 



At a. Strata dip 46° S.S.W. 

 *. ,, synclinal „ 



c. „ dip N.N.E. 



d. „ vertical „ 



e. „ dip 76° N.N.E. 



Cleavage dip 66°-60° S.S.W. 

 „ 72^ S.S.W. 

 S.S.W. 

 „ none or dip 80° S.S.W. 

 ,, vertical. 



The cleavage in all this tract dips to the S.S.W., at angles which upon the 

 * Geol. Proceedings, 1846. 



