2 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [ May l^, 



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 direc- 

 tion lies partly through the forest of Cerissy, across a tract which 

 preserves a very uniform level, and which is covered superficially 

 with accumulations of siliceous grits rounded into pebbles, mixed 

 with sand, clay and fragments of slate ; enough however is seen to 

 satisfy one that the slate system, without any change in character, is 

 carried on along the whole line of this section. 



Previous to my last visit to this part of France, I had considered that 

 the several small patches of coal, which have long been known to exist 

 in the departments of Calvados and La Manche, belonged to the true 

 carboniferous period. Considerations have since suggested themselves, 

 which induce me to think that they may be of a subsequent age. 



The strike of the slate rocks, in every place in which I could ob- 

 serve it, ranged steadily about east and west, whilst the apparent dip 

 or bedding (for I must admit that it is most difficult to determine 

 this) seemed northerly, and often highly inclined, as far as near 

 Littry. The coal-mines at this place are not situated, as descriptions 

 had led me to suppose, in a depression of the slate districts : it is 

 true, they occupy a low position with relation to some of the adja- 

 cent country, but their real position is at the extreme boundary of 

 the older rocks, and where the new red sandstone series abuts 

 against them. M. Herault has fully described this coal-field in the 

 ninth volume of the 'Annales des Mines,* and states that the works 

 are conducted on one seam only, which is about three feet thick : 

 this I had not any opportunity of verifying, but from the size of the 

 blocks of coal which are raised, the thickness of the seam must be 

 very considerable. The coal, or at least such as I saw, was of in- 

 ferior quality, dull, earthy and pyritous, with occasional compact 

 and shining seams in the plane of the bedding. My conviction is, that 

 the beds with which this coal is associated form no part of the older 

 group of strata (whether slates or siliceous grits), which are every- 

 where highly inclined, whilst the former are horizontal, or nearly so. 

 M. Herault, in the memoir above alluded to, gives sections of seve- 

 ral workings which appear to have been carried through the entire 

 thickness of this small coal-field, according to which its component 

 strata rest on the edges of highly inclined slates and grits, such as 

 compose the district to the north, preserving their east and west 

 strike beneath ; so that the coal strata must evidently have been 

 deposited subsequently to the elevation and disturbance of the older 

 series. I think that it is unnecessary to establish for all this part of 

 France any other division than that adopted by M. Dufrenoy ; and as 

 it is on the edges of the uppermost of the older beds that the carboni- 

 ferous strata of Littry are found, the latter cannot be identified with 

 the black carbonaceous slate of the department of La Manche, so rich 

 in Orthocerata and Crinoidea, or with the Anthracites of Brittany, 

 with which I thought at one time they might be contemporaneous*. 



* M. Alex. Brongniart refers the coal of Littry to his anthracitic group. See 

 Tableau des Terrains, p. 270. 



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