RANGE OF THE CHALK FORMATION. 177 



separating the northern and southern districts. 

 At Sandown Bay, we have seen the lower divi- 

 sions of the formation successively appearing in 

 the cliffs, in the anticlinal axis formed by the 

 elevation of the Weal den strata ; and in Compton 

 Bay a like elevation of these deposits in a similar 

 anticlinal system. 



At Culver Cliff, and from High Down to Comp- 

 ton Bay, the chalk downs, consisting of highly 

 inclined strata, form the sea-boundary ; but in 

 the middle of the Island, this chain is flanked on 

 the south by a denuded district of the lower 

 strata, which expands several miles, and is 

 succeeded by another system of downs formed 

 of horizontal beds of chalk. This range extends 

 from St. Catharine's to Shanklin Down, a distance 

 of six miles, (see the Map and section, PI. XX.). 

 Thus in travelling from the northern part of 

 the Island to the southern shore — as for ex- 

 ample from Ryde to Sandown, or from Calbourne 

 to Brixton — vertical and highly-inclined strata of 

 the flinty chalk are first passed over, and then the 

 firestone, gait, and greensand deposits ; the latter 

 composing the sea-cliffs from Sandown to Ather- 

 field, except where the fallen masses of the upper 

 beds strewn along the Undcrcliff conceal them from 

 observation. But in crossing the central district 



