MOUNTAIN LIMESTONE, DERBYSHIRE. 



93 



It is in the lower beds of mountain limestone that enormous natu- 

 ral caverns frequently occur : such are the well-known cavern near 

 Castleton, and Pool's-hole, near Buxton in Derbyshire ; and Yordas 

 Cave, under Whernside, in Craven. Gordal Scar and Weathercote 

 Cave, in the same district, cannot properly be called caverns, as they 

 are open to the day ; but the latter was probably once a cavern, of 

 which the roof has fallen in. In all these caverns, and others that 

 I have observed in this limestone, there is a stream of running water, 

 which is more or less copious in rainy or dry seasons. I am inclined 

 to believe that the caverns have been formed by the agency of water, 

 percolating through natural fissures, and in the lapse of ages exca- 

 vating the softer or more broken parts of the rock. The prodigious 

 force with which these subterranean streams rush through the open- 

 ings of some of these caverns, after continued rains, suggests the 

 probability of this mode of formation. The whole of that enormous 

 mass of limestone in Craven, from Ingleborough and Whernside to 

 Gordal, is intersected by perpendicular fissures, which are narrow at 

 the top, and become wider as they descend, through which the water 

 may be heard to run at a vast depth below. These unseen but ever- 

 active streams are slowly but progressively wearing down the internal 

 parts of these calcareous mountains, and depositing them in the sea. 



The mountain limestone of Derbyshire demands particular atten- 

 tion from the interesting geological phenomena which it presents ; 

 though it has been much visited and frequently described, I believe 

 the accounts hitherto given have been in some respects erroneous. 

 I revisited the country round Matlock soon after my return from the 

 Continent, and was then convinced that the structure of the calcareous 

 mountains had been mistaken, but the state of my health did not per- 

 mit me to pursue the enquiry. Since the publication of the third 

 edition of this work, I have examined this part of the country care- 

 fully, and shall briefly state the result of my observations. Mr. 

 Whitehurst has the merit of being the first observer who discovered 

 some of the leading features of the geology of this district : he bold- 

 ly pronounced that the beds of trap and amygdaloid, provincially 

 called Toadstone, which are interposed in the limestone, were vol- 

 canic lava, or at least had an igneous origin. This opinion was much 

 opposed at the time ; it is now confirmed by such a weight of evidence, 

 as to leave little doubt respecting its correctness, (See Chap. IX.) 

 though the facts and arguments by which Mr. Whitehurst's views 

 were then supported were in some respects fallacious. 



Mr. Farey, who followed Mr. Whitehurst, adopted the same views 

 of the general structure of the country, though his opinions respec- 

 ting the formation of the toadstone were entirely different ; he con- 

 sidered it to be an aqueous deposition, forming regular strata, like 

 those of sandstone in the coal measures. 



Mr. Whitehurst and Mr. Farey describe three beds of toadstone, 

 and four of limestone, in a descending series. 



