102 Rev. A. Sedgwick on the Geological Relations and 



Feet. Inches. 



3. Yellow indurated marl 4 



4. Stiff blue clay 2 6 



5. Meagre calcareous yellowish marl 1 



6. Impure earthy limestone 3 



Over the preceding came the regular beds of the superior limestone. 



3. Quarries behind the village of Askerne. 



Feet. Inches. 



1. Unctuous, red marl and fibrous gypsum. The upper part only is ex-1 



posed, and the thickness is unknown J 



2. Meagre, blue and red clay 2 



3. Striped, red and yellow sandy beds 3 



4. Red marl mixed with incoherent, yellow sand 3 



5. Grey, impure, sandy limestone marked with dendritic impressions 4 



Over the preceding came the regular beds of the upper limestone. 



All these sections are in the ascending order; and the two last only represent the highest part 

 of the deposit. 



Range and Extent, S^c. — These gypseous marls;, on the average probably 

 not more than thirty feet thick, are very well laid down by Mr. Smith : they 

 are, however, extended too far to the south ; and there are one or two slight 

 errors which I have endeavoured to correct in the accompanying maps*. It 

 is indeed often impossible to determine the range of these beds otherwise than 

 by connecting in imagination the several points where the plaster rock has 

 been excavated. In other places they occupy the base of a low escarpment 

 formed by the upper hmestone, and may under such circumstances be laid 

 down with much more precision. 



The fust indication of them in any decided form, is at the base of an obscure escarpment under 

 the village of Letwell in Yorkshire. To the south of this place they thin off, and probably dis- 

 appear ; at least there are no denudations which offer any proof of their continuity in that direc 

 tion t. 



Of their range towards the north it is not intended to offer many details; but the following 

 list of localities in which the gypseous marls have been excavated, may at least serve the purpose 

 of verification : 1. The bottom of the hill, half a mile west of Old-coats on the Firbeck road. 

 % In the mill-dam under Limestone Hill, three-quarters of a mile west of Tickhill. 3. Brick-pits 



* See Plate IV. Nos. 2. 3. and 4. 



t It may perhaps be proper to notice in this place a thick mass of red marl and sand, which 

 appears on the banks of the Worksop canal (about a mile and a half east of the escarpment of 

 magnesian limestone), and ranges towards the south. When I first saw it, I considered it as a 

 prolongation of the red gypseous marls described in the text. On examination, however, it not 

 only was found unconnected with them, but appeared to be in a lower part of the series. If it 

 be really imbedded in the formation, it must be regarded as a local deposit subordinate to the 

 yellow limestone, and may perhaps be brought into comparison with the anomalous red sandy 

 beds of Mansfield. It may, however, be an outlying mass of the upper red sandstone brought in 

 by a local depression of the dolomitic beds. 



