94 Prof. Sedgwick on the Carboniferous Chain 



I could have wished to extend the two diverging- sections, just described, as 

 far as the metalliferous hills between Arkendale and Swaledale ; but I am not 

 sufficiently acquainted with that region to represent the prolongation correctly. 

 I may, however, state in general terms, that the four-fathom limestone and 

 the twelve-fathom limestone range through the hills on both sides of Arken- 

 dale, and are among the best lead-bearing beds of the country. They are 

 known by the miners under the names underset lime and main lime, and are 

 immediately surmounted by a group about 100 feet in thickness (composed 

 of shale, chert, and gritstone, with some peculiar masses called red beds and 

 iron beds), which, on the whole, may be considered to represent the upper 

 shale of the general section (No. 12.). Over this group is a strong deposit of 

 coarse grit, upwards of sixty feet in thickness, which probably represents the 

 first millstone grit (No. 13.). 



The coarse gritstone last mentioned is surmounted by a very complex succes- 

 sion of deposits about 160 feet in thickness. In the lower part of this series we 

 have alternations of gritstone and shale, with a subordinate twelve-inch coal — 

 over these are alternations of chert and shale, with a bed of crow-limestone of 

 the extraordinary thickness of twelve feet — and the system terminates in a mass 

 of shale about eighty feet thick, containing three subordinate bands of impure 

 limestone. It has been stated above, that bands of crow-limestone are found, 

 here and there, subordinate to all the great shales of the carboniferous chain. 

 But their number, and the thickness of one of them, in so high a division of 

 the Arkendale section, must be considered anomalous. I have, however, little 

 hesitation in identifying this complex group (especially as it is immediately 

 surmounted by a deposit of millstone grit nearly 100 feet thick) with the 14th 

 division of the general section. 



The preceding details of this paper explain the structure of a part of the 

 carboniferous chain. Those which follow show the effects produced by the 

 prolongation of the great Craven fault, and the movements which took place 

 among some of the mineral masses when the chain was elevated. 



§ 4. Transverse Sections, from five points of the Longitudinal Section, 

 through the dislocated strata on the line of the Craven Fault*. 



The first transverse section (fig. 5.) commences from the top of Penigent, 

 and ranges (about south-west by west) through the village of Horton, over 

 Moughton Fell ; and thence over a second plateau of the Scar limestone, to 

 the calcareous hills immediately north-east of Clapham. 



* Plate VI. Transverse Sections (fig. 5. 6. 7. 8. 9.). 



