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454 454 THE GEOLOGIST. westward of the Needles, will not doubt but that the two promontories were once united, forming a rocky neck of land from Dorset to the Needles. This chain of chalk mi,2:ht, or might not, be so cleft in twain as to allow the rivers of Dorset and Wilts, to find a passage through them to the main ocean. My opinion, however, is that they had no such outlet, but that, at that far distant period, the entire drainage of more than two counties, embracing the rivers that join the sea at Poole and Christchurch, flowed through what is now called Christchurch Bay, down the Solent, and joined the sea at Spithead. According to this theory, the Solent was at that time an estuary some- what like the Southampton Water, having but one opening to the British Channel ; but of so much more importance than the latter as it was fed by a vastly greater flow of fresh water ; and it further supposes that the bed of the Solent was scooped out originally by a river, which from the extent of its drainage one may guess to have been little inferior to the Thames or the HumlDer. And this opinion acquires countenance from the circumstance that it accounts, in a most satisfactory way, for the equality of depth and breadth in the Solent Sea. Of course, according to this view, this sea would lose its original condition as an estuary at the time when the British Channel had so far made a breach through the chain of rocks connecting the Isle of Wight with Dorsetshire as to give an opening into itself for the Dorsetshire rivers, somewhere opposite to the town of Christ- church. From that time forth the Solent would become what it is at pre- sent, losing its character as an estuary, and assuming that of a long narrow sea. And at the same period, of course, the Isle of Wight would part with its peninsular character, and be severed from the mainland, but at a point far apart from that at which the severance is usually supposed to have taken place. The distant period at which such changes took place it would be hopeless to guess at, amid the dimness of the data on which calculations could be founded. It could not be less, however, than many thousands of years, seeing that since that time, the British Channel has not only made a broad breach of twenty miles through a chain of slowly yielding rocks, but has also pushed its way gradually across the broad extent of the Poole and Christchurch Bays. In conclusion, I would observe, that if your correspondent at Lyming- ton simply put his question about the separation of the Isle of Wight as an archaeological inquiry, I fear he will consider my answer to it as some- what dreamy. But I am confident, if he and others who may honour me with a careful perusal of my observations, are tolerably acquainted with the geology of the neighbourhood, and have had their minds disciplined for realizing the operations of nature on a large scale and through length- ened periods of time, they will perceive in this paper opinions indicative of more than novelty, having, as I believe, very important geological facts to uphold them. Yours, etc., W. Fox. Brixton, Isle of Wight, Nov. 8. TracTcs, Trails, and Imprints. Deae Sie, — At nearly the same time, probably, when t was pointing out the desirability of careful drawings and casts being made of the tracks and trails of living annelids, mollusks, insects, etc. (' Geologist,' No. 52, 138, April, 1862), for the guidance of the palaeontologist in decipher-