Geological Socieli/. 389 



argillaceous limestone which extends into terraces in some places 

 50 feet thick and half a mile in breadth. The Gait is probably not 

 more than 60 feet in its greatest thickness : it is widest on the E. of 

 Sutton, and from thence eastward varies in width from a few hun- 

 dred yards to a quarter of a mile. The upper, or ferruginous, por- 

 tion of the Shanklin sand, occupies the broadest space between the 

 chalk and the weald, and is from one to three miles in width, its 

 northern boundary forming a very distinct escarpment. The sur- 

 fiice of these sands is distinguished by its barrenness ; they vary 

 much in consistency and colour, and the lower beds especially, are 

 pervaded by seams of clay, and abound in a stone consisting of 

 coarse siliceous sand cemented by oxide of iron. The lower divi- 

 sion of this formation (green sandstone) has in some portions 

 a strong external resemblance to the stratum immediately be- 

 neath the chalk. It constitutes a fertile arable country, and affords 

 pure and copious springs. The upper part contains thick layers 

 and nodules of limestone, chert, and clay resembling fuller's earth. 

 The lower affords a compact building-stone, which has long been 

 ([uarried at Pulborough : but further west, these beds pass into 

 chert. This stratum has obviously suffered great disturbance; and 

 one of its natural chasms, forming the valley of Greenhurst, and 

 about 4 miles in length, points tov/ards the outlet ofArun, and 

 might probably be taken advantage of to connect that river with 

 the Adur. The demarcation between the lower part of the Weald 

 claij and the subjacent Hastings sands, is not well defined in the 

 tract which the author describes. A considerable bed of sand oc- 

 curs within the clay at its upper part ; after this comes in a bed of 

 <' Sus.<;ex marble;" and lower down in the clay, a second layer of 

 sand containing siliceous grit in thin beds ; beneath which the prin- 

 cipal beds of Sussex marble (about 18 inches in thickness) occur; 

 and these are finally succeeded by blue, brown, and red clay, and 

 micaceous sand, the commencement of the forest ridge. 



The author gives a particular description of the defile of the 

 Arun, the principal outlet of the Weald in the south of Sussex. 

 This river traverses about 15 miles of a country almost mountain- 

 ous, cutting across the ridges of the sand and the chalk escarp- 

 ment nearly at right angles to the valley of the Weald. The gorge, 

 where it enters the green sandstone, is more than 400 or 500 

 yards in width at the bottom ; and the banks rise quickly to the 

 height of about 200 feet on the east ; and on the west to about 400 

 or 5!jU feet. At Bury and Amberly, where the river penetrates the 

 clialk, the hills are 600 or 700 feet high; the ravine having all the 

 characters of a fissure. And as the strata, in several cases of this 

 description, rise on both sides towards the crack, the author sup- 

 [)oses that the channels now existing on the surface, have been 

 produced by the operation ofsome internal forces by which the beds 

 were broken up and elevated ; and that the drainage of the country 

 by tiie present outlets, can be thus explained ; without having re- 

 course to a debacle, or to denuding operations : and he supports 

 this hypothesis by reference to the local features of tlie country, 

 illustrated by sections. 



ASTRO- 



