﻿11 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NOV. 6, 



in the Bulletin of the French Geological Society*. But near as it is 

 to the much-frequented baths of Vichy, no one had previously dis- 

 covered the organic remains to which I shall presently advert, and 

 which enable us for the first time to assign the old rocks in question 

 to their real place in geological history. In making this announce- 

 ment I would however state, that organic remains are so scarce, and 

 the rocks containing them have so much an " azoic " aspect, that 

 I would rather attribute my discovery of fossils to a happy accident, 

 than pretend to throw any discredit on my precursors. 



The lacustrine limestones and marls of the Limagne d'Auvergne 

 are prolonged northward by Vichy and Cusset to Billy, on the right 

 bank of the AUier, about twenty-five miles south of Moulin s, where 

 they constitute hills of some hundred feet in height, the horizontal 

 strata of which stand out to the low, flat, and younger region of the 

 Bourbonnais and Orleanais, without any barrier or edge whatever of 

 older formations. 



In the hills east of Vichy, however, and near Cusset, the lacustrine 

 limestone is flanked by schists penetrated by porphyry and other in- 

 trusive rocks, which form the northernmost extremity of the chain 

 called the Forez. Both these classes of rock are well exposed on the 

 banks of the small river Sichon, above Cusset, where their outlines 

 present a picturesque gorge daily frequented by parties of pleasure 

 from Vichy. In ascending the Sichon from Cusset, the first promi- 

 nent objects are bluff porphyries, which jut out through the verdant 

 slopes and rise above the rich and umbrageous walnut-trees of this 

 pretty sinuous valley. These porphyries, for the most part quartzi- 

 ferous, are of red, pink, and dark grey colours. In some of them the 

 crystals of felspar are so large as to liken them to the Norwegian 

 ' rhomb-porphyr ' of Von Buch. In parts, however, the porphyry 

 passes into and becomes a coarse-grained greenstone, which is largely 

 quarried, and in other places into a compact felspar rock or clay- 

 stone. On the whole, these bosses are void of anything approaching 

 to stratification, and are traversed by innumerable cross fractures and 

 fissures. They are indeed manifestly intrusive, as respects the 

 schistose strata with which they are associated ; for in numberless 

 places the latter are seen to be irregularly broken through and cut 

 up into wedge-shaped masses which are isolated in porphyry. 



The schists have on the whole a direction from S.S.E. to N.N.W.j 

 but the strike is very devious, owing to the above-mentioned intru- 

 sions ; whilst the strata dip at every possible angle from verticality 

 downwards. The schist resembles some of the older palaeozoic strata 

 of the British Isles which have been much affected by igneous erup- 

 tion. Its aspect led me at first to suppose that it might prove to be 

 of Lower Silurian age. In parts it is affected by a rude slaty cleavage, 

 as indicated by coarse and irregular planes of fracture transverse to 

 the laminse of deposit. These, and the predominance of joints, the 

 faces of which are coloured red by oxide of iron, occasion the stone to 

 break into multitudes of small rhombs. In such a rock — even in 



* Visquenel sur les . environs de Vichy. Bull. Soc. Geol. Fr., 1st ser. vol. xiv. 

 p. 145. 



