Otterborne, on the southern slope of that same ridge, we lose the chalk, because, the country lowering, we enter into an alluvial basin; in which lies Southampton, and which probably extends as far as to Carisbrook a little beyond Newport, in the Isle of Wight. There we meet with the belt of chalk hills before mentioned, and again on the southern slope we enter at Shorwell, a sandy basin, till we come no the southern coast of the isle which is chiefly composed of calcareous sandstone, chert, and coarse shelly limestone.
We shall find that the same arrangement prevails about Corfe Castle, and there indeed we may fairly say that the shallow inner harbour of Poole lies in the bottom of the trough of sand which rests on the acclivities of Corfe Castle chalk-hills. Were the sea to force itself a passage somewhere between Lulworth and Wareham, (situated at the head of Poole harbour) would not then the Isle of Purbeck improperly called so now, become a true island? and would not then its formation be owing to a cause exactly like that which I have ventured to suppose, has formed the present Isle of Wight?
I shall close these observations by saying, that if we take a comprehensive view of the southern counties of England, from the east of Kent to the Land's End, we may safely assert, that there are very few countries which, within such limits, can boast of so varied and regular a succession of rocks, from those which are reckoned by most geologists to be of the latest formation, to those which belong to the oldest.
