Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/308

 at Newhaven and Chimting Castle, appear again on the opposite shores of France in the same relative position.

I am indebted to the kindness of M. Brongniart for the following section near Dieppe, which forms a valuable link connecting the formations above the chalk in France with those of the same era in the south of England. He has observed the following strata in the perpendicular cliff under the light-house of St. Margaret, on the west of Dieppe, counting upwards from the lowest stratum:


 * 1) Chalk.
 * 2) Sand and sandstone in thick beds containing concretions of the same substance.
 * 3) Strata of plastic clay, impure and containing lignite much charged with iron pyrites, also oysters and cerithia, both in beds and irregularly disseminated.
 * 4) Alluvium.

These strata M. Brongniart considers as identical with beds of the plastic clay formation in many other parts of France, particularly at Marly, and in the Soissonnois, where the same organic remains occupy strata similarly disposed and identical with those near Dieppe.

I shall add a few more circumstances of resemblance in the French and English formations of plastic clay.

It is noted by M. M. Cuvier and Brongniart, that in the basin of Paris the sand between the chalk and plastic clay, though very pure, is often coloured red or bluish grey. In the latter state it occurs at Woolwich, Lewisham, and Newhaven. We have already (p. 280.) stated the analogy which the Reading oyster bed bears to the brecciated bed next above the chalk at Meudon. Of the plastic clay it is also stated by the same authority that it often consists of two beds separated from each other by a stratum of sand. The lowest of these two being properly the pure plastic clay, while the upper is coarse,