OOLITE. m 



darker colour, approaching to that of flint, but curiously mottled with 

 small brownish or purplish spots, with a minute light speck in the cen- 

 tre of each. Some of the nodules are fine hexagon madrepores, which 

 have been met with, not of a pyriform shape, but in flat masses. The 

 occurrence of chert in limestone is considered as analogous to that of 

 flint in chalk ; and the analogy is borne out by the fact, that chert 

 also occurs in some limestone strata in thin beds or seams, as flint does 

 in the chalk.* 



The numerous vertical fissures in the oolite and the beds imme- 

 diately beneath it, are receptacles for water, as well as for marl and 

 spar. Most of the rain that falls on the oolite hills, particularly those 

 on the north side of the vale of Pickering, is immediately imbibed by 

 the light soil that covers them, and sinking into the fissures, nms 

 down the declivity of the hills in subterranean streams, which burst; 

 out at the foot of them in copious springs, nay, even in mighty tor- 

 rents. Hence these hills are remarkably dry, and a great part of the 

 valleys that intersect them are streamless. It is rare to find a spring^ 

 amongst them in any elevated situation, and wells of water cannot be 

 obtained without sinking to a great depth. The well at Cropton is 

 no less than 216 feet deep. Hence also, as all the springs from these 

 hills break out at the base of their decKvities, where they descend 

 into the vale of Pickering, a chain of towns and villages skirts the foot 

 of the hills all aronnd, built at these springs for the sake of their co- 

 pious waters. 



At the mouths of several of these springs, particularly the smaller 

 springs, we find incrustations of moss and other vegetable substances,- 

 on which the waters have deposited the calcareous matter with whicl> 

 they are impregnated. Many of the springs, however, are too copi- 

 ous, and burst forth too violently, to admit of such depositions. At, 



*■ Geological Transactions, IV. p. 420. Bakewell's Geology, p. 388». 



