24 PICTURESQUE SKETCHES 



stances. From its frequently assuming the appear- 

 ance of clay slate, and being indistinguishable from 

 that rock except by the presence of fossils, it may be 

 supposed that the materials of which it is for the 

 most part formed were obtained from older, and 

 probably from igneous, rocks pounded still more 

 finely at the bottom of water, and forming fresh com- 

 binations, often marked by the presence of sand ob- 

 tained from the quartz of the granite, and also oc- 

 casionally distinguished by the presence of mica. 



In those parts of England and Wales in which these 

 rocks have been discovered, they have been found to 

 exhibit indications of very extensive disturbance, and, 

 in some cases, seem to have been deposited alternately 

 with great masses of igneous rock poured out like lava 

 from a volcano, but erupted through the bed of the 

 ocean, and soon covered up with new deposits. Be- 

 sides disturbances of this kind, these same rocks have 

 in North Wales been subjected to so much squeezing, 

 under a great pressure from above, that they are twist- 

 ed into folds repeated several times, just as a number 

 of pieces of cloth might be thrown into wave-like folds 

 if squeezed by lateral pressure, with a heavy weight 

 resting upon the upper surface. No description, how- 

 ever, can at all do justice to the singular complica- 

 tion thus introduced into the huge masses of hard and 

 tough rock. In one place the strata are snapped 

 asunder and displaced, in another they are bent 

 nearly double like sheets of paper. Here the slaty 

 beds are contorted into the most strange and violent 

 curves; there, the opposite cliffs of a narrow glen 

 exhibit them torn asunder like fragments of soft wood 

 or semi-tenacious paste. 



