internal Structure of the Magnesian Limestone. 103 



west of Wadworth*. 4. In wells at Loversal, Balby, and various places near the Don. 5. A pit 

 near the south-west end of Cusworth Park. 6. In wells near Red House. 7. West side of Camps, 

 mount and Clay-flats. 8. The west side of the village of Askern, where the marls are brought up 

 by a fault. 9. The south end of Norton. 10. On both sides of the Went below Little Smeaton. 

 11. Pits on the west side of the road near Grove Hall. 12. Great canal under Knottingley. 

 13. Rail. roads from the Air to the limeworks of Fairburn, &c. 14. Plaster-pit Hill &c. 



From the last-mentioned place, the gypseous marls range across the north road nearly four 

 miles from Ferry Bridge, and are continued in a very obscure form, and apparently interrupted 

 by some great faults, to the south-west side of Sherburn, where they have been proved in wells. 

 In this part of the range they seem gradually to thin off; and at the village of Towton they 

 are, if I mistake not, represented by a bed of stiff blue clay not more than two feet thick. There 

 are some obscure indications of them in association with outlying masses of the upper limestone 

 at Dalton lane, and one or two other places north of Bramham; but they have noc, I believe 

 been discovered in any part of the formation of magnesian limestone to the north of the Wharfe. 



§ 3. Upper thin-bedded Limestone, sometimes without Magnesia. 



The gypseous marls last described are surmounted throughout their range 

 by a grey thin-bedded limestone, which forms the highest tier of the dolomitic 

 series resting on the back of the other parts of the formation, and dipping 

 (generally at a very low angle) into the plain of the new red sandstone. The 

 thin-bedded structure is universal, not unusually passing into a structure 

 which is slaty and sometimes foliated. Between these beds, and even between 

 the foliations, there is generally interposed a very thin plate of bluish grey or 

 greenish grey marl; and when these marls become so thick as to assume the 

 character of beds (which is, however, rarely the case), they have then gene- 

 rally a tinge of red or purple. When seen in a quarry or natural section, the 

 thinner beds have an irregular shattered appearance : and when one of them 

 is struck with a hammer, it generally falls into pieces at a number of natural 

 joints, which are coated over with beautiful, black, dendritic or stellated im- 

 pressions. 



The deposit is traversed by a great many nearly perpendicular fissures or 

 small faults, on the opposite sides of which the beds have seldom the same 

 exact inclination. From the appearance of the large denudations near Ferry 

 Bridge, as well as in other places, it would seem that the system here de- 

 scribed had been partially broken up after its deposition ; and that the dis- 

 turbing forces not being able to raise the incoherent beds into continuous 

 undulations, had snapped them asunder at all the points of greatest flexuref. 



» See Plate IV. No. 4. 



t To the remark in the text there are one or two striking exceptions ; but they apply to the 

 greater dislocations, which are not noticed in this place. See Plate IV. sec. 1., and Plate VII. 

 fig. 6. (Wadworth and Knottingley.) 



