■ ■» 









: 



P 





TJPPEK 



CLEAVAGE, ETC. 125 



degrees of hardness and coarseness. Where the slate joins 



the coarser grit x the sudden change in the direction of Ga ^ry. 



the cleavage is especially remarkable. In the slaty portion Wall - ca ^46. 



the cleavage and bedding form an average angle of about 



46°. In the coarser grit x the angle is about 16°. 



35. — Small specimen from the same locality, showing the 

 same kind of phenomena. 



36. — Coarse green and purple slate, Cambrian, Llyn 



Padarn, Llanberis. Shows 



stratification 



green and ash grey, traversed by coarse cleavage. 



37. — Sandy slate, Lisburne Mines Cardiganshire. Map 

 57. The red lines show the direction of the planes of 



bedding. 



38. 



vonshire. Map 

 the beds. The 



•>f 



rfaces at the sides are planes of 

 and front planes are joints. 

 ate, Ffestiniog Slate Quarries, Caernar- 

 The red lines show the direction of 



faces of the slate (like all true slates) 



39. 



b 



Pern 



Probably derived from the coarse Cambrian slaty beds 

 south of St. David's. The green and purple lines show 

 lines of bedding, and the cleavage which cuts them at an 

 angle of about 30°, is very coarse. 



40. — Slate, Westmo 



Exhibiting well marked 



ashy grey. 



f ivavy stratify 



b 



faults, 



it is remarkable that the downthrow is on the opposite 

 side from that which is usually the case in nature on a 



large scale. The polished front surface is a cleavage- 

 plane. 



41. — Banded slaty rock, showing lines of bedding Joints, 

 and cleavage. The 



front 



and back are cleavage planes. 

 J-ne upper and under surfaces are planes of bedding, and 



other parallel beds, in narrow bands, lie between, and the 

 sides are joints. 



