1823.] Mr. Farey on the Pontefract Sandstone Rock. 211 



unconformable rock, somewhere about the junction of the sheets 

 of Mr. Smith's map, perhaps, leaving then my first coal shale 

 on the surface, in contact with and passing under the Pontefract 

 rock ; and it is this coal shale which, in such case, produces 

 the Harrowgate medicinal spaws : unless indeed both the second 

 and the first grit rocks have passed under the Pontefract uncon- 

 formable rock, before we arrive so far north as these spaws?; 

 under which last circumstances, these celebrated springs will be 

 referable to my " limestone shate." 



But whichever of these may, on a rigid investigation, prove 

 to be the fact, it will, I think, certainly result, that a strata ridge 

 (which may not be easily definable by a line on the map, or 

 without careful levellings, owing to this ridge in the upper 

 measures, having an irregular rounding summit), will be found 

 emerging from under the edge of the Pontefract rock, some- 

 where not far from Thornton Chapel ; and, proceeding west- 

 ward by Pateley Bridge, there, either my shale limestone or the 

 first limestone rock emerges on the surface of this ridge in a 

 local denudation, extending to near Raven's Cross : thence this 

 strata ridge probably declines southward, and ranges through 

 the smaller denudated tract of limestone, north-east of Barden; 

 then bending again northward, it probably, near Burnsal, enters 

 a more extensive denudated tract, proceeds, perhaps, by Khkl y- 

 mallam Dale, and then bends so much northward as to pass 

 Settle, and proceeds on the north of Clapham and Ingleton ; 

 passing thus north-east of, and occasioning the dip south-west- 

 ward into the Black Burton coal-field. 



Generally speaking, the strata ridge last described should be 

 considered as the boundary northward, of the great Yorkshire 

 coal-field; and that to the northward of this strata ridge, a 

 district of undulating strata commences, and the same are dis- 

 posed in several strata troughs, ranging eastward and westward, 

 and are separated by corresponding strata ridges, through the 

 remainder of the county ; and, perhaps, it is the same in the 

 south-western parts of Durham. On this principle I should, if 

 entering n a survey of the local coal-fields of this northern part 

 of Yorkshire, search northward of Thornton Chapel, before con- 

 jectured to stand on the great strata ridge, for the emerging of 

 the first grit rock* (dipping north-eastward, and covered more 

 northerly by the first coal shalef) from under the unconformable 



* My first grit rock may probably be comprised in Nos. 101 to 95 in Mr. W. Fors- 

 tei's " Section." 



r Part of my first coal shale probably appears in his Nos. 0-L to 91, and the remain- 

 der of this shale is omitted, 1 think ; especially as Mr. F. himself, in p. 93, suspects 

 some strata to be here omitted ; but the number and thickness of these (including, pro- 

 bably, I think, my second and third grit rocks, and the intervening second coal shale* 

 are, perhaps, much more considerably than he is aware of. Where is the ganuttr 

 found? or its peculiar species of leafy reedlf, or the two species of marine sbeVs ? 

 enumerated in p. 243, vol. i. of Mr. Sowerby's " Mineral Conchology," in the coun- 

 tii i of Durham or Northumberland J; and is this stone there any where applied to the 

 making of roads? 



