about 30 feet cut through in 1868, but no longer shown in 1870, making a total thickness to be described of about 127 feet (as shown in fig. 1).
These beds have a nearly uniform dip to S.S.W., or more nearly south, of from 2-1/2 to 3 degrees. Their rise, measured horizontally, varies from 1 in 20 to 1 in 25. Their total rise, within the limit of the excavations from south to north rather exceeds 100 feet.
These strata admit of grouping into four more or less marked divisions, characterized partly by mineral structure, and in part also by a change of fauna. They may be described as follows, commencing with the lowest beds : —
1. Clays and sandy clays with Pyrites 36
2. Argillaceous sands with Dentalium 25
3. Sands with Lingula 8
4. Clays with Cyprina and sandy clays 55
I propose to give in this place a broad outline of these groups, reserving to an appendix the details of the sections and a full list of fossils.
(1) Clays and Sandy Clays with Pyrites. — This group includes : —
ft.
A. Stiff blue clay 10 to 15
B. Hard sandy clay with Pyrites 15
C. Argillaceous sands with thin layers of blue clay and grains and nodules of Pyrites 10
The blue clay of this group was exposed in a deep cutting in 1868. It contained masses of drifted wood perforated by Teredo ; and specimens of a large Ostrea, referred by Mr. Edwards to Ostrea gigantica, Sol. A mass of wood was obtained to which several of these Oysters were attached.
Fig. 1.-Section through Line ofn Excavations of Portsmouth.
