EXPLANATION OF THE PLATES. xix
giving way, a part of the cliff falls down, and the fragments are worked by themasons into the forms proper for several purposes. In the rock on the foregroundover which you walk, may be seen numerous fragments of fossil bone imbedded.
About the middle of the bay under C, the limestone becomes curiously bent andtwisted in the most fantastical manner, evidently shewing the whole to have beenat some period in a pliable state, and to have been subjected to elevation or subsidenceaccompanied by lateral pressure. The dip of the whole, however, is to the north,so that the mason recognises among the uppermost beds on the opposite side of thebay, those which are the lowest on this side. Under B the cliffs are composed ofclay, a bed of which is inferior to the limestone series, and in this, in the quarries,masses of gypsum are found. At Durlstone head, under A, the Purbeck limestoneagain occurs in the same disturbed manner. See pages 171, 172.
Plate XXX. Contorted Strata, Durlstone Bay. T. W. del. \ ^
This sketch represents one of the numerous contortions to be seen in this bay. It isa circumstance worthy of remark, both here and in other parts of the Purbeck series,that the thinnest beds are generally the most bent. See page 172.
Plate XXXI. Breccia, Durlstone Head. T. W. del. V ^1$ /
At Durlstone head the Purbeck beds are not only bent and broken, but the fragmentshave been cemented together again into a singular sort of breccia. Large masses ofthis lie at the bottom of the cliff, and form a very curious subject for geologicalspeculation. See page 173.
Plate XXXII. No. 1 . Durlstone Head. T. W. del. " v * ^
The rock in the foreground of this sketch is a bituminous limestone, divided intosepta by numerous veins of calcareous spar, and is the same bed as the uppermostof the oolite series at Tillywhim and the isle of Portland. The upper surface of itappears to have been subjected to some action that has worn it into hollows, previousto the placing on it of the Purbeck beds that now cover it. These Purbeck beds areviolently contorted and broken, and again cemented into the breccia mentioned above.
See page 173.
No. 2. Windspit quarries. T. W. del.
These quarries consist of a series of excavations in the face of the cliff betweenrillywhim and St. Adhelm’s head. The cliff is here of great height, and consistsof an oolite, being the same formation as the isle of Portland. The stone workedhere is somewhat harder than the Portland stone, but not quite so white. It is con-sidered as rather more durable. It was in that part of the cliff covered by spray,