internal Structure of the Magnesian Limestone. 107 



raation, the highest and lowest divisions of which are more compact and thin- 

 bedded than the great central mass, and generally contain a less proportion of 

 magnesia. There are some parts of Yorkshire north of the Wharfe where the 

 highest portions of the magnesian limestone have this compact and thin- 

 bedded character ; yet in the absence of the lower red marl, it is difficult to 

 find their exact relations. In some instances they are probably contempora- 

 neous with the deposit here described, and they may at least be conveniently 

 classed with it. 



In this view of the subject, I would refer to this upper system a thin-bedded 

 light-coloured, magnesian limestone of Copgrave and Goldisborough ; also a 

 similarly bedded, yellowish brown and dark smoke-grey limestone, which 

 appears in several places on the back of the formation near the villages of 

 Well, Snape, and Watlass*. 



Between Nosterfield and Well, there is a system of beds in the position 

 above described (ranging about N.N.W. and S.S.E., in length about a mile, 

 and in breadth about a quarter of a mile), and of so very peculiar a character 

 as to require a more detailed notice. As they dip about S.E. at a considerable 

 angle, the most northern quarry on the range lays bare the lowest beds, and 

 shows that they rest immediately upon the yellow limestone, without the in- 

 tervention of any red marl. 



First Section. — From Welsea quarry, a quarter of a mile south of Well, beginning with the 



lowest beds visible and ascending, ^ 



° Feet. Inches. 



1. Hard, yellow, magnesian limestone ] q 



2. Several thin beds of ditto 1 o 



3. Fine, yellow dolomite, like the dolomites of the carboniferous limestone. . 6 



4. A system of beds of very deep smokc-grey, and dark greyish blue colour . 30 

 The greatest part of the system (No. 4.) is composed of incoherent, shattered beds resembling 



a highly calcareous, indurated shale ; but there are a few beds, each about a foot thick, of closer 

 texture, some of which are fetid, and cannot be distinguished from carboniferous limestone. One 

 of these beds, near the top, is traversed by many compressed cylindrical stems about one inch and 

 a half in diameter, but without any external markings to indicate their origin. 



Second Section, in the ascending order. — From a quarry (called Seven-acre) further on the 

 dip of the beds. p 



1. Strong, yellow, cellular, magnesian limestone forming the base of the quarry. . — 



2. Thin, shattered beds of a brownish blue colour, and with thin seams of marl . . 12 



3. Earthy, yellowish beds 3 or 4 



4. Dark brown and black shale highly calcareous and semi-indurated 1 



* Among the thin beds of Watlass quarry are some which exhibit traces of globular concre- 

 tions like those of Fulwell Hill ; and some of the bands of marl arc dark and carbonaceous, 



P 9. 



