446 



THE GEOLOGIST. 



limestone, divided by tliin layers of sandstone and " plates," and one bed of 

 coal, wliicb is not continuous. The upper limestone — under the names of 

 Camfell-, Main-, Parkhead-, and Twelve-fathom-limestone — is one of the most 

 constant in the district. The greatest thickness of this group is . 200 feet. 



(h) group of flagstones, called the " Hawes-flagstones," from their great 

 development at the head of Wensleydale ; it contains one strong band of 

 limestone, and a great thickness of gritstones and " plates," very varied in their 



character. The thickness of these flagstones is 500 to 600 feet. 



(c) The "Black-limestone" group containing two well marked beds of 

 limestones, the lower one of which produces the grey encrinital marble of 

 Dent, with " plates" and grits. Its thickness is .... 200 to 300 feet. 



3rd. Below this is the lower " Scar-limestone," of a much more homo- 

 genous character, the thickness of which, as it forms the bottom-rock of 

 most of the valleys, has not been accurately measured. It cannot, however, 



be less than . . 500 feet. 



The general dip of this series is south-east, and in following the beds in that 

 direction to their disappearance under the magnesian limestone and New Red 

 sandstone, the thickness of groups a, b, and c becomes gradually^ less by the 

 obliteration of the two lower series first; and finally by the thiiming out and 

 complete disappearance of the upper one, until in Wliarfedale and Nidderdale 

 the Millstone-grit reposes directly upon the lower "Scar-limestone," which 

 has increased in thickness until, from being the bottom-rock of Wensleydale, 

 it almost reaches the top of Great Whernside, and forms the sides of the deep 

 vaUey of the Wharfe. 



But another cause has been at work to alter the face of the country besides 

 the gradual change in the thickness of the beds. On a ciuwe, drawn from 

 Settle to Harrogate, at the foot of the dales that faU to the south from the 

 chain of hills skii'ting the southern side of Wensleydale, the lower "Scar- 

 limestone" appears to abut against, instead of underlying, the Millstone-grit, 

 This is caused by a downthrow of the latter, on the line called the " Craven- 

 fault," which beginning near Kirkby Londsdale, where the limestone and the 



the east, in which direction it breaks up the limestone itself, as in the district 

 of _ Craven, and stiU further east disturbs the position of the limestone and the 

 MiUstone-grit, until at Greenliow-hill the last traces of it are exposed before it 

 disappears under the Magnesian-limestone, which being a later formation has 

 covered up aU tokens of the disturbance. 



Wlienever the streams run through the upper " Scar-limestones" their 

 general course is eastwardly, with a slight tendency to curve to the south ; but 

 as soon as these beds disappear, and the lower " Scar-limestone" comes upper- 

 most, we find that the valleys turn southward until they reach the line of the 

 Craven-fault, when they follow again the natural dip oi* the beds. This fault 

 thus becomes the cause of much of the variety in the character of the 

 scenery of these Yorkshire dales. 



Our road lay out of Wensleydale, up one of its lateral vaUeys called Bishop- 

 dale, and over Kidstone's Pass, a route practicable for carriages, which can be 

 said neither of the pass to the right out of Raydale, over Stake Pell, nor 

 of tliat to the left out of Coverdale, over Buckdeu Pike, although both are 

 sometimes attempted. 



All the valleys out of Wensleydale are either destitute of roads leading 

 southward, or the passes are excessively steep on their southern faces. This 

 fact is connected with another in the physical geography of tiie district ; viz., 

 that Wensleydale is bounded to the north by an unbroken chain of liills, while 

 on the south five large valleys run into it. Swaledale and Teesdale are 

 equally destitute of dii'ect lateral valleys from either the south or north. 



altered, may be foUowed towards 



