worn, at Ramsholt, and abundance of corals not of European forms at Orford, where it is used as a limestone.[1]
Below the Crag deposits of Essex and Suffolk the London clay is seen very extensively in the cliffs, and along the eastern valleys. It is singularly poor in organic remains; now and then a chelonian skeleton appears in the nodules of impure carbonate of lime which yield the 'Roman Cement.' These are now scarce on the shore and in the cliffs, and are obtained by dredging at small distances from the land. In the cliffs at Felixston, faults appear in this clay.
A deposit of tertiary shells in green and irony sands, and in blue clay, occurs at Bridlington in Yorkshire; it probably is of the age of the mammaliferous crag, and is covered by northern drift. The most general view of the English marine tertiaries shows sands to be more extensively diffused than clays; the latter are almost limited to the southern basins; the former are no where wholly deficient, and their lower green portions very characteristic. The calcareous crag is merely a local product.
Turning now to the district where first the genius of Cuvier awakened the philosophical study of the tertiary strata,—the basin of Paris,—we obtain highly interesting results for comparison with the English series and those of the south of France, Italy, and the Danube.
The Parisian series is quintuple, but only two of the terms are marine; two are decidedly of freshwater origin as to the materials (one certainly even lacustrine); the fifth (and lowest) is rather to be viewed as a troubled estuary or river deposit, and may be united with the lower marine formation. The whole stands in general terms according to the example on p. 257.; but we must observe that the several groups are partially mingled with one another by intercalation: there are, in fact, many marine and many freshwater strata,
- ↑ The crag has been investigated with great success by Charlesworth, Wood, Lyeil, Henslow, and Colchester. At the base of the red crag lie the valuable bands of phosphatic nodules.
