258 Dr. Berger on the Geology of some Parts 



V. Coarse Shelly Limestone (Calcaire grossier).\ 



This kind of rock I am rather anxious, to introduce here, because 

 it seems to constitute a formation by itself, which, I believe, was 

 first pointed out by M. Brongniart, who has given us some very 

 valuable information on the subject. This variety of limestone was 

 thought to be very scarce in England, but I am now disposed to believe, 

 that upon a further examination, it will be found to occupy a great 

 extent of country, and will, by many persons perhaps, be considered 

 as a continuation of the same strata or beds which exist on the oppo- 

 site coast of France. I have observed it in the southern part of the 

 Isle of Wight called the under cliffy in several places of the Isle of 

 Purbeck, in the Isle of Portland, and, from some specimens which I 

 have seen at the Geological Society's apartments, I have but very 

 little doubt, that it exists also in the counties of Surry, Sussex, Ox- 

 ford, Rutland, and Somerset. In France, it forms the bottom or 

 basis of several extensive plains ; such as that of the neighbourhood 

 of Paris, and that of Caen in Normandy. 



I have seen it alternating with a calcareous sandstone, with the 

 oolithe, (oviform limestone of Kirwan), and with marl: passages of it 

 may be traced on one hand to the calcareous sandstone, and on the 

 other to the oviform limestone. At the quarry of Tilly Wym by 

 Seacombe Cliff, to the east of St. Aldham's Head, and at Chapman s 

 Pool near Encombe, as also in the Isle of Portland, it includes patches 

 of a compact limestone of a greyish, or dark blue colour, which be- 

 comes harder as it passes gradually into a state of complete flint or 



+ Chaux carbonatee grossiere ; pierre a btilir ; plerre cle taillc when in large blocks, 

 and md'e'llon, when it is ia smaller masses. Brongniart, Traite dc Alineralogicj torn. 1. 

 p. 204. 



