Dr. FiTTON on the Strata below the Chalk. 245 



lions, so as to overlie the latter, and beyond them come into immediate 

 contact with the subjacent clays. 



The small map, Plate VII. fig. 3, gives a plan of this valley on a larger 

 scale than that of Plate IX., and the Sections ab to gh, PI. X. a.. No. 13., 

 further illustrate its structure: — the strata being the Chalk, — Upper green- 

 sand, — traces of the Lower green-sand, and of the upper members of the 

 Wealden; beneath which the Purbeck and Portland formations are more 

 fully disclosed. 



(127.) Chalk. — The beds at Harnham Hill, immediately on the south of 

 Salisbury, are inclined to the north ; and about a mile to the west of that hill 

 a curved ridge, or horseshoe, formed of the upper chalk, seems to be the first 

 divarication of the strata which bound the Vale of Wardour*. It therefore 

 deserves inquiry whether the continuation of the fissure produced by an 

 upheaving on the east of this point, may not be discoverable in the space 

 between Salisbury and the head of the Wealden denudation. The southern 

 limb of the chalk forms a continuous and lofty ridge from Harnham, 

 through Compton Hill and Chiselbury, to White Sheet Hill, around the base 

 of which the Upper green-sand occupies the whole space from Berwick 

 St. John's to Shaftesbury, the escarpment of the latter formation, which 

 is the immediate boundary of the vale, being continued all along the foot 

 of the chalk range, and rising from beneath it towards the north. 



On the summit of the ridge at Chiselbury, the chalk includes black flints in spongiform nodules : 

 the Down slopes northward at an angle of upv/ards of 26° ; and at its foot there is a depression 

 or trough. The lower and marly chalk form a ridge at Hoopside, about 200 feet above the 

 stream at its base, and perhaps 100 below the summit of the highest range, which as the name in- 

 dicates is curved, and nearly parallel to the curve of the upper chalk at the Race-course. The 

 hill in Wilton Park belongs to the upper chalk, which there crosses the stream of the Nadder, 

 passing through North Burcombe and thence towards the north of west, to form the higher downs, 

 on the north of the valley, at some distance from the ridge of the sands. The lower chalk and 

 chalk marl constitute an intermediate tract, in several places outtopped by the sand ridge. In 

 the height above South Burcombe, is chalk with veins and nodules of flint ; and nearly on a 

 level with the river, north-west of Hoopside, the Upper green-sand comes in. 



The succession from the flinty chalk to the Upper green-sand, on the north of the valley, is 

 well seen in the road from Hindon to Fonthill Giffbrd. The ridge on which the archway stands, 

 at the entrance to Fonthill Park, being chalk with large flint nodules, exposed in a pit imme- 

 diately without the plantations, dipping north about 12°, and separated by a depression from the 

 ridge of the Upper green-sand, which is here very low. 



* The Map, Plate VII. fig. 3, unfortunately, was engraved before I had observed the structure 

 described in the text, so that the points here referred to are not included in it : but the features 

 are well represented in the Ordnance Map; the aid of which, indeed, is almost necessary through- 

 out these pages, to understand what is stated respecting the structure of the country. 



