ox CLEAVAGE AND FOLIATION IN ROCKS. 



379 



further northward 

 dip of the beds i 



Fiff. 13. 



, at a 

 rresu 



great quarry the cleavage dip is southward 52°, the 

 lar, but northerly about 60°; and still farther the 



Fig. 14. 



■~^-J 





cleavage dip is southerly 50°, 40°, 

 38°, — which last observation was 

 made at Grange. 



These results are all on the 

 north side of the line of vertical 

 cleavage at Watendlath, and in 

 the middle slate series. In the 

 Watendlath Valley and in the 

 fells between it and Borrowdale, 

 the phaenoinena are much less 

 regular. In the Skiddaw slate 

 which appear near Grange, the 

 cleavage surfaces are sometimes 

 twisted so as to be partly vertical, 

 and partly dipping south, with an 

 irregular strike N, 25° E., which 

 differs from the strike of Wat- 

 endlath, Bo wderstone,andGrange 

 above 40°. When the beds and 

 the cleavage dip in opposite di- 

 rections, the angle included be- 

 tween the planes is in several 

 cases about 68°; when the dip 

 is in i\\&s'jme direction, the clea- 

 vage at the highest angle, the in- 

 cluded angle is often about 32°. 

 When the beds are nearly verti- 

 cal, the cleavage is nearly coin- 

 cident with the strata. I have 

 seen no horizontal cleavage in 

 the Lake district*. 



In the still more interesting 

 sections on this page (Diagrams 

 13 and 14), Mr. Sharpe repre- 

 sents the bedding and the clea- 

 vage in a line of country crossing 

 the strikes of both, from Helvel- 

 lyn to Bowness. In Diagram 13 

 the strata are seen to be bent an- 

 ticiinally and synclinally in Hel- 

 vellyn, — raised in a broad arch 

 north of Grasmere, and from 

 thence subject only to smaller 

 folds, dipping generally south- 

 south-eastward. In Diagram 14, 

 the cleavage dips are shown for 

 the same region, these being per- 



* Prof. Sedgwick has obliged me by 

 a note confirming this statement in re- 

 gard to the Lake district, but he has 

 observed horizontal cleavage in Corn- 

 wall and Wales, and Mr. Sharpe records 

 it in Devonshire. 



