﻿16 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Nov. 6, 



descends. Whilst on a visit to the ancient castle of Busset, where I 

 was hospitably entertained by its noble possessor*, I found that the 

 plateaux on both banks of the Sichon were penetrated by numerous 

 bosses of trap rock. Porphyries of different character, some of them 

 very granitoid, are seen in contact with highly jaspidified and altered 

 schists. In the whole ascent of the river to Ferrieres, numerous 

 minor domes of porphyry appear, which have thrown the strata into 

 such numberless flexures, and have so dislocated and wrenched them 

 in divergent directions, that all regularity of strike and dip is obli- 

 terated. To search in such a district for any order of formations 

 was impracticable ; but I came away disposed to think, that the 

 marble limestone (once partially worked) at Ferrieres was a mere 

 repetition of the less altered calcareous courses near the Ardoisiere of 

 Cusset. I could detect no marked change in the aspect of the rocks, 

 and the carbonaceous black schists which had been dug into in search 

 of coal, further led me to suppose, that the same formation was con- 

 tinued into the higher parts of the Forez by repeated undulations. 



An excursion along the western edge of the Forez to the nourishing 

 manufacturing town of Thiers confirmed this view. That town is built 

 on a steep rocky slope facing the plain of the great Limagne d'Auvergne, 

 and is watered by a rapid torrent which descends into the valley by a 

 picturesque, deep gorge. There again we have (particularly under the 

 lofty church of St. Gene) the very same phsenomena that occur all 

 along the banks of the Sichon, thirty miles to the north. At Thiers, 

 indeed, the features are grander. Like the Scottish varieties of por- 

 phyry of Loch Fyne, and other places, some of the intrusive rocks of 

 the Forez may almost be termed granites ; others are fine-grained and 

 pass into greenstone. As to the schists which they penetrate, it is 

 impossible to distinguish them from the similarly broken strata of 

 the Sichon, except that, if possible, these of Thiers are still more 

 altered. 



I further endeavoured, by a traverse across the lacustrine depo- 

 sits to Gannat, and thence by Ebreuil, to the beautiful castle of 

 De Veaucef, to detect if possible something of organic life in the 

 ancient schists (thrown off by the granite) which form the western 

 boundary of the great trough of the Limagne d'Auvergne. But I 

 had little time at my command, and I must leave to other observers 

 the credit of detecting fossils, if such there be, in the schists, whether 

 argillaceous or micaceous, which range southwards from Ebreuil, by 

 Pont Gibaud, into the region of M. Dor and the Cantal. I satis- 

 fied myself, however, in an excursion westwards, that many of the 

 beds of the coal-field of St. Eloy, near Montaigu, are made up out 

 of the detritus of still older schists and their quartz veins. I am 

 unprepared to say positively whether this coal tract, as well as other 

 numerous little coal deposits that extend along the western side of 

 the M. Dor into the Cantal (and which I examined in company with 

 Sir C: Lyell in the year 1828), are or are not of the same date as the 

 carboniferous schists of the Sichon ; but I am disposed to think that 



* General le Comte de Bourbon-Busset. 

 t The seat of the Baron De Veauce. 



