Outlines of Geology. 237 



tion. These veins, which generally run N. and S., often disturb 

 the parallelism of the strata; and, intersecting them, as well as 

 the metallic veins, give rise to much confusion and disturbance. 

 In the district we are now upon, there is an instance of the ele- 

 vation of the strata to more than two fathoms upon the side of 

 such a cross vein. The contents of these veins are very mis- 

 cellaneous ; and where the material they are filled with is much 

 harder and more durable than the assailed strata, their course is 

 often perceptible upon the weather-worn surface of the strata, 

 sections, or precipices, they traverse. Such is the cross vein in 

 these lead-measures, called theJDevil's Back-bone, forming a ridge 

 that may be traced a considerable distance along the strata through 

 which it passes. 



The limestone district of Derbyshire presents us with so many 

 points of interest and importance, that much more might be said 

 upon it than our time here admits. I shall only touch upon a 

 few of its leading features. Castleton is at its N. point, and it 

 extends about twenty-five miles S. to Weaver-hill. Its breadth 

 is very irregular, but, I believe, nowhere exceeds about twenty 

 miles. Its eastern end forms the delightful and varied scenery 

 of Matlock, so strangely counterpoised by the dull monotony of 

 Buxton at its western edge. Its north-western extremity is cele- 

 brated for the wonders of the peak. 



In accounting for the varied aspect of this district, we may be 

 assisted by recollecting, first, that the strata of limestone differ 

 considerably from each other, and that beds of another ^species of 

 rock intervene, which is provincially called toadstone, and that 

 the respective edges of these strata come to the surface ; and 

 secondly, that the whole country is there traversed by a great 

 fault or dislocation of the strata. 



Mr. Farey has described the Derby district as composed of 

 four beds of limestone and three of intervening toadstone. The 

 upper bed of limestone is in part bituminous, and contains nodules 

 of chert arranged nearly as flints in chalk. It contains entro- 

 chites and various shells, often exhibited in relief upon its weather- 

 worn surface. Beneath it the rock contains beds of magnesian 



Vol. XX. S 



