Mr. Lonsdale on the Oolitic District of Bath. 



261 



Sandstone, abounding with fossils 3 feet. 



Sand 4 feet. 



Clay. 



The Oxford clay composes a plain of great variableness of breadth. At 

 Melksham it is about six miles broad^ but at Laycock it is scarcely one. The 

 western boundary has been already traced under the head Cornbrash ; the 

 eastern, rauff-es about one-third from the summit of the coral-ra"-hiIls : and 

 passes from the neighbourhood of Ly nham^ by Charlcot, Bremhill Wick, Studley, 

 Redhill, Bovvden Hill, Spy-Park, Chitway, Sandridge, Nonsuch, Bromham, 

 Rovvde Hill, Seend Bridge, Sell's Green, Baldham Mill, Hinton, Cold Harbour, 

 Stourton Farm, Abury Common, Rovvde Ash ton Park, West Ashton, Hey- 

 wood House, Brook Farm, Brumridge Farm, Dilton, the Black Dog, Berkley 

 Lodge, Heath -House-Farm, and Corsely, to Chapmanslade. 



Corral Rag. 



The coral rag formation in Dorsetshire, as described by the Rev. W. D. Co- 

 nybeare in the "Outlines*," and by Professor Sedgwick in the Annals of Phi- 

 losophy f; and in the Vale of Pickering by Mr. PhilHps;];, consists of two beds 

 of sand, separated by a third of limestone. In Wiltshire a similar arrange- 

 ment exists, but the upper sand is for the greater part wanting ; and where it 

 occurs, it is thin and of little apparent importance. The following table 

 exhibits a general type of the Wiltshire beds. 



1. Upper calca- 

 reous g 



lea- "1 

 nt§/ 



2. Coral rag 



3. Clay 



4. Lower calcare. 



ous grit§ . . . 



Sand 



J'erruginous clay J- 



Perishable freestone 



Rubbly oolite 



Irregular beds of Poly- "( 

 paria j 



Sand, with beds of calca-") 

 reous grit and impure i> 

 limestone J 



Thickness. Localities. 



f Between West Ashton and Dunge, 

 \ and between Keevil and Rey Down. 

 /Near Steeple Ashton and Westbury 

 I Field. 



Calne. 



Calne. Steeple Ashton. 



< Calne. Steeple Ashton, 

 Chilvester Hill, near Calne. 

 Spirthill, Bremhill, Sandridge, Stud- 



io ft. 



10 ft. 



40 ft. 

 40 ft. 



40 ft. 



40 ft.? 



soft. 



{ 



ley, &c. &c. 



1 . The sand (1 a) is of a fine grain and of a ferruginous colour. The clay 

 (1 b) which underlies the sand, is slightly oolitic, and contains at Steeple 

 Ashton numerous specimens oi Belemnites ahhreviatus, a Mya, and occasion- 



* p. 191 note, and p. 192. f For the year 1824. 



X Phil. Mag. vol. iii. p. 248. Geol. of Yorkshire, p. 32. 

 § This term is adopted from Mr. Phillips. 



