448 Mr, P. J. Martin on the Anticlinal Line of 



north and south of it. As I have elsewhere said, it is variable 

 in its character. At the points indicated, as above, by the 

 remarkable eminences of Portsdown and High Down, the dip into 

 the northern synclinal is gentle and easy ; but it is in otliers 

 more abrupt and inchning to the character of what Mr. Hopkins 

 calls flexure*, like the one-sided saddle at Farnham and the 

 Hogsback in Surrey, or even to direct upcast or fault ; for in its 

 passage from Portsdown eastward by Emsworth, I find that on 

 the south side of the hamlet of Prinstcd, wells reach the chalk 

 through ten or twelve feet of gravel; whilst on the north side of the 

 same, within the short distance of 200 yards, wells are sunk 60 or 

 70 feet in London clay, and then water is only procured by perco- 

 lation from above. I have not at present evidence to prove that 

 this line of elevation has so much the character of a '^ fault '' or 

 sharp flexure elsewhere, but there is good reason to believe that 

 this is very much the case in all the line of country through 

 which it can be traced between Portsdown and High Down. How- 

 ever this may be, it is certain that all the flat country south of 

 the Downs, ranging from Bedhampton at the foot of Portsdown 

 to Brighton, including Hayling and Thorney Islands, the estuary 

 of Chichester Harbour, and the peninsula of Selsey, is intersected 

 by this chalk ridge with a trough of tertiaries on each side. The 

 importance of this arrangement cannot be too highly appreciated, 

 as bringing so great an accession to that category of parallel 

 linings or foldings of which the great anticlinal is composed, and 

 carrying the phsenomena of denudation along with it so far out 

 of the range of the Weald Valley. This great tract of country 

 has been so completely rasee, it is so flat and so copiously be- 

 strewed with drift, and so little raised above the level of the sea, 

 as to have impressed some early observers with the notion of a 

 sea-bed comparatively modern, of which the chalk downs were 

 the clifi'-bound coast. It is unnecessary to say that this idea is 

 here entirely repudiated. The enormous quantity of angular flint, 

 the entire removal of the chalk to which that flint belonged, the 

 thick beds of fertile loams and brick-earths manufactured on 

 the spot and mixed up with these angular flints, the absence of 

 rounded gravel except such as has been obviously derived from 

 the eocene immediately contiguous to the chalk, — all bespeak a 

 tumultuary activity by far transcending the erosion and attrition 

 of an ordinary sea-board. 



The drift of this flat and remarkable district admits of a natural 

 division into two kinds — the diluvial, and the boulder or glacial. 

 The former is the loamy drift with angular flints, as before said, 

 so copiously spread over the northern division. The southern, 

 comprising the peninsula of Selsey, and all the coast of Brackles- 

 * Transactions of the Geological Society, vol. vii.p. 17. 



