106 Rev. A. Sedgwick on the Geological Relations and 



Feet. Inches. 



5. A hard, yellowish brown dolomite, in texture like No. 1., but here and"! ^ 



there passing into an earthy form J 



6. Very thin beds with partings of marl ; irregularly slaty or foliated ; 1 g q 



general characters like those described under No. 2 / 



It is seen in the preceding section how the regular dolomites alternate with the peculiar, thin 

 beds of this part of the series. Some of the thin beds, however, effervesce feebly with acids, and 

 contain a small quantity of magnesia. 



The alternations are still more remarkable in the quarries near Old-coats a few miles further 

 to the south. We there meet with all the modifications of structure which have been just de- 

 scribed : the thin beds are in some rare instances studded over with minute globular concretions; 

 and one nearly compact bed contains a great many small specks of galena. Before reaching 

 Carlton this deposit becomes so changed, that it is not easily distinguished from the lower por- 

 tions of the magnesian series. 



4th. Askerne. — At this place there is a very fine section of the upper limestone. Many por- 

 tions of these quarries are magnesian ; but we meet with no yellow, crystalline dolomites like those 

 of Tickhill. Some of the beds are of a reddish colour, and are almost irreducible in the kilns. 

 The workmen have learned to separate those portions which burn to a cold lime from the more 

 caustic magnesian beds with which they alternate. 



These sections, together with the general notices which precede them, are, I hope, sufficient 

 for the description of this highest member of the dolomitic series. 



Range — Outliers — Probable Extension of the Deposit towards the North, 8^c. 



These upper beds first appear on the west side of the village of Carlton near Worksop ; but 

 in following them towards the north their relations, for two or three miles, are rather obscure. 

 Before reaching the village of Old-coats, they put on a very characteristic form ; and to the west 

 of that place they are bounded by a regular escarpment resting upon the lower gypseous marls. 

 From the neighbourhood of this place they may, with very limited exceptions, be easily traced to 

 the banks of the Wharfe. Their western boundary in this long range is determined by the 

 gypseous marls above described ; and their eastern boundary has already been sketched out in 

 the former part of this paper*. The escarpment seems to die away in the alluvial plain of the 

 Wharfe near Grimstone, and the upper limestone sinks below the surface : but a small patch 

 (which may, perhaps, be considered as an outlier) appears some miles further up the river, 

 occupies the right bank for a few hundred yards near Paper-mill Bar, and seems to range in a 

 very obscure form towards the right bank of the Bramham river. 



There are three small outliers of this upper limestone : one forming the cap of the low ridge 

 immediately south-west of Ferry Bridge ; another about two hundred yards from the great North 

 road, close to the cross road leading off to Kirk Smeaton ; and a third near the south-west corner 

 of Wetherby Grange Park ; and there may be more small patches of the same kind which have 

 escaped notice. 



As this limestone is certainly prolonged beyond the limits of the lower 

 gypseous marls, it becomes a question of some importance how far we can 

 trace it in the range of the formation to the north of the Wharfe. In a general 

 point of view the whole dolomitic series may be described as a complex for- 



* See page 51. 



