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CORBESPONDENCE. 453 Michael's) on their own coast, to which such minerals could easily have been conveyed, and which, in its connection with the mainland, answers pretty closely to the historian's remarks ; and further, as I know of no argument worth listening to why the miners of Cornwall should have transported their tin to the Isle of Wight for exportation, — on all these several grounds, I think one may safely conclude that neither Diodorus, nor any other writer of note, has left any evidencv whatsoever about the fordableness of the Solent within historical times. The severance of this island from the mainland, it appears to me, was effected under very unusual circumstances, and at a very distant period. The present channel of the Solent, being pretty nearly equally deep and equally broad throughout its entire length of twelve or fourteen miles, proves at once that it was not formed in the usual way of island-severing channels, that is, by gradual encroachments of the sea on the two opposite sides of a narrow neck of land. If so formed, the middle part of the channel would naturally have been both narrower and shallower than the two mouths that first admitted the tide towards it ; but this is not the case. Nor are there any important indestructible obstructing rocks on either side of the channel that could account for this peculiar formation. It is to be accounted for, therefore, not by the excavations of a gradually ap- proaching sea, but, as I shall hereafter have to attempt to show, by its being originally the trunk or outlet of a very considerable river. Again, at the western mouth of the Soleut, there is almost an immea- surable accumulation of rolled flints, with which are mingled a sufficient sprinkling of fragmental fossil shells of various genera and species to show us from whence the whole mass was originally transported. This accumu- lation forms a sort of natural breakwater, two miles in length, one hundred yards in breadth, and many feet in thickness, extending between the main- land at Milford and a point beyond midchannel, where Hurst Castle was erected three centuries ago. Where the castle stands, this bank of flints becomes expanded so as to cover a circular space of fully twenty acres. Now all this enormous accumulation of flints, together with another one probably much larger on the island side of the main channel, and lying under the sea, in front of Alum Bay and the Needles, are formed of drift and broken fossils from the Barton beds ; the fossils themselves plainly pointing to the formation whence the whole mass was derived. It would add too much to the length of my paper, to account for this vast lodgment of drift around the mouth of the Solent ; neither is this needful as respects the objects of my remarks : only I would have my renders to understand that it depends upon the flow of tide through the channel of the Solent. And when it is remembered that the annual supply of drift along the Bar- ton cliffs is comparatively small, it will then be seen that it must have re- quired a period reaching far back in time to gather together the vast accu- mulations referred to above, and consequently they may be regarded in themselves as visible and lasting memorials of the very great antiquity of the separation of the Isle of Wight from the mainland- Nay, I will venture to hazard an opinion, even though I stand without geological authorities to support me, that will place the date of the forma- tion of the Solent Sea still further back in the dimness of the past ; an opi- nion to which both the peculiarities of the channel itself above referred to, and the geological formation of the surrounding country, bear very strong testimony. Whoever as a geologist examines the vertical strata of the chalk at the Needles, nay, and throughout the whole length of the Isle of Wight, and the strata of the same rock in exactly the same unusual posi- tion on the bold white cliff on the Dorsetshire coast some twenty miles