30 Prof. BuciiLAND and Mr. De la Beche on the 



liills within its area. The valleys are usually cut down to the slaty forest 

 marble beds and their associated clays. 



On the norths and east^ and south, it is entirely surrounded by, and dips 

 beneath, the Oxford clay ; on the west it is terminated by the back-water of 

 the Fleet, cutting* it in an oblique line for about four miles, from the village 

 of East Fleet to the Swanery of Abbotsbury. It has been already stated, 

 that it constitutes the axis or central arch of the Weymouth district, upon 

 each side of which, as on a saddle, all the more recent formations successively 

 repose. 



After a slight depression beneath the surface at Abbotsbury, the forest 

 marble and its clays, or in most cases the clays without the marble, reappear 

 in strength in the Vale of Bredy, occupying an extent of surface about eight 

 miles long and four miles broad; bounded on the east and north by the over- 

 hanging escarpments of chalk and greensand ; on the south by the sea and 

 Chesil Bank, and on the west by the subjacent strata of inferior oolite near 

 Burton Bradstock and Bridport. Throughout all this Vale of Bredy, the main 

 dip of this strata is towards the north. 



Inferior Oolite. 



Along the whole coast of Dorset, and indeed the whole south coast of En- 

 gland, there is a total absence of Bath oolite ; but the inferior oolite occurs in 

 tlie vicinity of Bridport, attaining a thickness of about 300 feet, and occupying 

 the clilfs for two miles east, and three miles west, of Bridport Harbour. The 

 summits of the highest hilis around the town are composed of the superior 

 strata of this formation, consisting of coarsely oolitic yellow limestone, resem- 

 bling that of Dundry Hill near Bristol, irregularly interspersed with oolitic 

 grains of hydrate of iron, as at Bayeux in Normandy : the most extensive 

 (juarries in these upper strata of the inferior oolite, are at the summit of 

 Chideock Hill, on the west of Bridport ; these are wrought in a light brown 

 limestone full of large and small ferruginous grains ; a few beds also abound in 

 minute veins and cells lined with hydrate of iron. One stratum on this hill is in 

 great measure composed of fragments of Pentacrinite, others contain a variety 

 of organic remains, — Ammonites, Nautili, Belemnites, several Pectens, a large 

 Lima, CucuUaea, Plagiostoma, Modiola, several species of Terebratula, and 

 fossil wood*. 



Beneath this coarse limestone is a series of brown and yellow loam and 

 sands, highly micaceous, and containing, iu their upper region, strata of cal- 



* Tlie oolite of Chideock Hill contains caverns, but no bones have yet been noticed in tliem ; 

 in the same oolite beds at Burton Cliff, there are inaccessible fissures filled with diluvium. 



