Excavation of' Valleys. 37 



Uh, These alluvial deposites are covered by a mass of tufa- 

 ceoiis conglomerate, or rather breccia*, very irregular in thick- 

 ness, containing some pebbles of quartz and granite, but diff'ei-ing 

 from the inferior alluvium by the abundance of angular trachy- 

 tic fragments, and a tufaceous cement, uniting the whole into a 

 solid mass. 



We now proceed to the northern and western side of the same 

 hill, where a steep escarpement faces the river Couze at the vil- 

 lage of Perrier. Here the geologist is presented with a magni- 

 ficent vertical section of alternating beds of alluvion, and tra- 

 chytic breccias, perhaps without parallel ; the whole forming a 

 covering more than three hundred feet in thickness to the ter- 

 tiary marls on which the town of Perrier stands. In the allu- 

 vial beds alternating with, and beneath, this enormous mass, 

 Messieurs Jobert and Croizet, have detected animal remains 

 similar to those found near Bouladef, and in vast quantities. 



A few hundred yards west of the locality last mentioned, the 

 hill bends slightly round, so as to afford a section almost trans- 

 verse to the preceding, and clearly to exhibit the superposition 

 of the deposites already described, to the basaltic mass which caps 

 the tertiary marls. That mass is seen to pass down under beds 

 of pumice and gravel, which slope in the same direction, but 

 less rapidly. Some of them thin out before reaching the basalt, 

 and they are all thinner towards their termination upwards. 

 This is precisely the disposition which these strata may be sup- 

 posed to have taken, if they filled up a lake, of which the basalt 

 formed one of the lateral barriers. 



At the village of Pardines, a few hundred yards farther to the 

 N.W., the side of the hill may be seen still more completely 

 divested of its alluvial coverings. This exposure is in a great 

 measure due to the great land-slip of Pardines, which hap- 



• We prefer the term breccias for these aggregates of shapeless and angu- 

 lar fragments of trachyte, because conglomerate is so generally applied to 

 those puddingstones which consist of rounded pebbles cemented together by 

 a base of sand or other matter; but we should state that our breccias are the 

 same as the tufaceous conglomerates of many writers on Auvergiic, and cor- 

 respond exactly in character with the trachylic conglomerates described by 

 Beudant as of such great extent in Hungary. 



t Sec Plate II. 



