internal Structure of the Magnesian Limestone. 57 



dip*. The indications exhibited by the coal works near Skegby (and we might also add by the 

 whole coal-field extending from Pinxton to Tibshelf) lead to the same conclusion. 



4. There can, I think, be no doubt that the magnificent terrace which ranges by Palterton 

 and Bolsover, rests upon a productive part of the Derbyshire coal strata. Until, however the 

 neighbouring coal-field is more nearly exhausted, it is not probable that any great work wi'll be 

 conducted within the limits of the yellow limestone. A bed of impure coal was formerly worked 

 under the limestone at Orscroft ; and a similar impure pyrltous bed is worked at Clown close to 

 the terrace of the limestone, under which all the inferior strata are carried by a gentle dip to the 

 south-east t. At Knitacre Hill (about a mile and a half to the north-east of Barlborough) there 

 are the remains of ancient coal-works considerably to the east of the terrace. 



It is sufficiently evident from this short statement, that the magnesian limestone stretches over 

 a part of the great coal formations of Derbyshire and Nottinghamshire : it also seems to follow 

 that the same deposit must be unconformable to them ; for the coal-beds which range immediately 

 under the escarpment are not all of the same age, but belong to different successive portions of a 

 great deposit, and therefore cannot in any sense be considered as contemporaneous. 



5. After the magnesian limestone enters the county of York, it contiuues for about thirty miles 

 to agree in its range, its dip, and its inclination, so exactly with the neighbouring coal-measures 

 that there seems to be little evidence in the district south of Pontefract to prove any want of con- 

 formity between the two formations. The limestone rests upon the highest known portion of the 

 Yorkshire field, which contains some thin beds of coal generally impure and pyritous. Beds of 

 this kind have been worked in several pits sunk on the west side of the magnesian terrace and 

 in a few instances the works have been conducted beneath it. At Micklebring (a village on the 

 escarpment of the limestone about three miles south of Conisburgh) a swiftly burning impure coal 

 about seventeen inches thick, has been worked to a considerable extent. Some old shafts appear 

 to have been sunk through the western skirt of the limestone ; but the present works are pro- 

 longed under it by means of a level which enters the hill side below the village. The same bed 

 of coal appears formerly to have been worked at the bottom of the hill on the road from Clifton 

 to Conisburgh : and on the other side of the Don, between Metton and Barnborough, several 

 shafts have been sunk upon a bed of coal, which agrees both in its quality and in its relations 

 with that at Micklebring]:. A similar bed was reached a few years since by a boring, which 

 was made on Upton Moor near the edge of the limestone. Lastly, a bed of coal of like quality, 



* In this part of the field the best bed of coal is about five feet thick ; over it is half a yard of 

 clunch (indurated slate clay), and above the clunch is a bed of soft coal thirty inches thick. The 

 old pit sunk down to this deposit was six hundred yards west of the new shaft, and only 161 yards 

 deep ; from which it appears that the dip of the strata is about one yard in thirty. (See 

 Plate V. fig. 1.) 



t The following is a register of the strata sunk through at the Clown coal-shaft. 



1 . Vegetable matter and rubble 5 feet. 



2. Yellow clay 5 



3. Red sand 6 



4. Marl, with a thin bed of iron-stone 6 



5. Blue bind (a variety of soft unctuous slate-clay) 21 



6. Dark shale (sometimes used for black chalk) 9 



7. Pyritous coal 4 feet 4 inches. 



Nos. 2. and 3. probably belong to the marl beds which separate the magnesian limestone from 



the true coal-measures. The impure coal would not have been worth extracting had it not been 

 near the surface. 



+ A further account of the section of Micklebring will be given in a subsequent part of this 

 paper. 



VOL. III. — SECOND SERIES. I 



