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Show 280 ENCROACHMENTS OF TilE SEA ON and of the Needles on the west; while Sandown Bay on the one ·de and Compton Bay on the other, have been hollowed out of Sl ' h' h . .c • the softer sands and argillaceous strata, w IC are In1enor to the chalk. The same phenomena are repeated in the Isle of Purbeck, where the line of vertical chalk forms the projecting promontory of Handfast Point; and .swanage Bay marks the deep excavation made by the waves m the softer strata, corw responding to those of Sandown Bay. The entrance of the Channel called the Solent is becoming broader by the waste of the cliff's in Colwc1l Bay~ it is crossed for more than two-thirds of its width by the shmgle bank of Hurst Castle, which is about seventy yards broad, and twel~e feet high presentinrr an inclined plane to the west. This singular bar consists 0 of a bed of rounded chalk flints, ~estin~ on an arrrillaceous base, always covered by the sea. 'I he flmts and ab few other pebbles, inter,mixed, arc exclusively det·ived from the waste of Bordwell, and other cliffs to the westward, where fresh-water marls, capped with a covering of chalk flints from five to fifty feet thick, are rapidly undermined. In the great storm of November, 18~4, this bank of shingle was moved bodily forwards for forty yards towards the n.ortheast; and certain piles which served to mark the bound~r1es. of two manQrs were found, after the storm, on the opposite side of the bar. At the same time many acres of pasture land were covered by shingle, on the farm of Westover, near Lyx_ning~on. This bar probably marks the line where the opposmg tides meet, for there is a second, or half-tide, of eighteen inches, three hours after the regular tide in this channel. The cliffs between Hurst Shingle Bar and the mouth of the Stour and Avon arc und~rmined continually. Within the memory of persons now living, it has been nec~~sary thrice to remove the coast-road farther inland. The tradition, ther:fore, is probably true, that the church of Bordwell was once m ~he middle of that parish, although now very near the sea. 1~e promontory of Christ Church Head gives way slowly. It ~s the only point between Lymington and Poole Harbour wheie any hard stony masses occur in the cliffs. Five laye~s of large ferruginous concretions, somewhat like the sept~na ?f the London clay have occasioned a resistance at this pomt, to which we rna; ascribe the existence of this headland. In the TilE SOUTH COAST OF ENGLAND. 281 mean time, the waves have cut deeply into the soft sands and loam of Poole ~ay; and, after severe frosts, great land-slips take place, which by degrees become enlarrred into narrow ravines, or chines, as they are called, with ver~ical sides. One o~ th.ese chines, near Boscomb, has been deepened twenty feet w1thm a few ~ears. At the head of each there is a spring, the water$ of whiCh hav7 been ~hiefly instrumental in producing these narrow excavatiOns, which are sometimes from one hundred to one hundred and :fifty feet deep. T~e peninsulas of Purbeck and Portland arc continually wastmg away. In the latter, the soft argillaceous substratum (Kimmeridge clay) hastens the dilapidation of the superincumbent mass of limestone. In 1665, the cliffs adjoining the principal quarries gave way to the extent of one hundred yards, and fell into the sea· and in December, 1734, a slide to the extent of one hundred and fifty yards occurred on the cast side of the isle, by which several skeletons, buried between slabs of stone, were discovered. But a much more memorable occurrence of this nature inl79~, is thus described in Hutchins's History of Dorsetshire: " Early in the morning the road was observed to crack : this continued increasing, and before two o'clock the ground had sunk several feet, and was in one continued motion, but attended with no other noise than what was occasioned by the separation of the roots and brambles, and now and then a falling. rock. At night it seemed to stop a little, but soon moved a~am; and before morning, the ground, from the top of the cbff ~o the water-side, had sunk in some places fifty feet perpe? dicular. The extent of ground that moved was about a mtle and a quarter from north to south, and six hundred yards from east to west." ~ortland i~ connected with the main land by the Chesil Bank, a ndge of shmgle about seventeen miles in length, and, in most place.s, ne~rl! a quarter of a mile in breadth. The pebbles formmg thts Immense barrier are chiefly of limestone; but there are many of quartz, jasper, chert, and other substances, all l~os~l~ thrown together. What is singular, they gradually dm~m1sh in size, from the Portland end of the bank to that which attaches to the main land. The formation of this bar may probably be ascribed, like that of Hurst Castle, to a meet.. |