On the Coal Beds of Lower Normandy.

Abstract

Several tours in Lower Normandy have enabled me to observe the geological structure of that district, and to trace the distribution of fossil forms through several groups of strata. It was my intention to have embodied these facts in two separate memoirs, of which one would have related to the Palaeozoic group, and the other to the Cretaceous; but in the autumn of 1844 I revisited many parts of Belgium and Rhenish Prussia, and have, in consequence, been induced to alter my original plan of describing the Cotentin and part of Calvados separately; and instead of this I now propose to lay before the Society two general memoirs on those two groups, as they are developed in Western Europe. I have therefore detached the short notice of the Littry and Plessis coal-fields, which form the subject of the present communication, from the memoir of which it originally formed part. My last visit to Lower Normandy was in the autumn of 1843. I had then expected to find a line of section taken northwards from about Balleroy as far as the coal-mines of Littry would have given a good ascending section, and have exhibited the distinct relations of a true carboniferous series, to the older slate rocks of Calvados : such however was not the case. The road in this direction lies partly through the forest of Cerissy, across a tract which preserves a very uniform level, and which is covered superficially with acculumations of siliceous grits rounded into pebbles, mixed