Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/212



The last of these highly inclined strata at the base of their western escarpment are generally covered by beds of a very different character, which lie in horizontal layers upon the broken basset edges of the lowest beds of sandstone. This arrangement of the two formations may be observed to the south of the Avon on the towing-path just where the beds of sandstone terminate, and to the north of the river near to Sneed Park; at these places the sandstone is covered by horizontal beds, of that kind of breccia which I shall presently describe. These horizontal beds form a series of low hillocks extending from where the sandstone terminates to within two miles of the Severn. They are best observed on the southern bank of the Avon, at Hung-road near to Crokerne Pill, where their section is exposed at low tide in a perpendicular cliff nearly 60 feet high. The beds consist of a red loamy earth and of breccia arranged in the following order.

The upper and lower beds of breccia present nearly the same characters. They both consist of calcareous and siliceous fragments cemented together by a calcareous base, having cavities in it, which are filled with calcareous and siliceous crystals, and sometimes with sulphate of strontian. The calcareous crystals have either the form of the primitive rhomb, or of the dog's-tooth spar, and are sometimes covered over with an incrustation of smaller crystals of carbonate of lime. The quartz is crystallized in six-sided pyramids. Besides the sulphate of strontian which is found crystallized in the cavities in small quantity, it occurs in large masses either imbedded in the breccia, or lying between the two beds of it. It occurs in blocks of