1845.] LYELL ON LAVA CURRENTS IN AUVERGNE. 75 



and this accumulation accompanied by occasional volcanic out- 

 breaks near the surface, producing merely local dislocation, probably 

 followed by a general depression. 



Secondly, The contemporaneous disturbance and upheaval of the 

 whole district by the intrusion of a volcanic rock in nearly parallel 

 lines from south-east to north-west, causing an inclination in the 

 stratified rocks to the north and north-west, and followed by great 

 denudation. 



And thirdly, The gradual elevation of the whole country, con- 

 tinued to the present time, by which the present physical appear- 

 ances were produced by the denudation of the softer rocks, leaving 

 the porphyry in elevated mountain ridges (which have been since 

 materially acted upon by the atmosphere), and leaving insulated 

 masses of the volcanic rock of the earliest period. 



November 19, 1845. 

 The following communications were read : — 



1 . On the Age of the newest Lava Current o/" Auvergne, with remarks 

 on some Tertiary Fossils of that Country. By Charles Lyell, 

 Esq., M.A., F.R.S., F.G.S. &c. 



Until my recent visit to Auvergne in 1 843, I was never able to 

 hear of the discovery of any fossils so connected with the most mo- 

 dern class of volcanic cones and currents of lava, as to enable us to 

 assign to them any other than a very indefinite geological date. 

 But when in the course of my last tour I inquired of the Abbe 

 Croizet, well known as an eminent comparative osteologist, if he 

 had yet found any fossil bones or shells in gravel lying immediately 

 under the newest lava-streams, he replied that he had recently met 

 with a great number of mammiferous remains at Nechers, in a bed 

 of reddish sandy clay, which rested against the side of the long and 

 narrow coulee which has issued from the Puy de Tartaret. This 

 hill, as the readers of Scrope's ' Geology of Auvergne ' will re- 

 member, is one which, by its position in the bottom of a valley at 

 the lower end of the Lac de Chambon, and by the integrity of its 

 heap of loose scoriae, has all the characters belonging to the class of 

 most modern cones, those which have been least altered by time. 

 The lava issuing from it forms a narrow stripe, occupying for more 

 than thirteen miles the bottom of the valley in which the river Couze 

 de Chambon flows, and at length terminating at the small town of 

 Nechers, about six miles north-west of Issoire. At a short distance 

 above the end of the current in the suburbs of the town, the lava at 

 its side presents a steep and often perpendicular face, twenty -five ^eet 

 in height towards the river, a meadow only intervening between it and 

 the banks of the Couze. Most of the bones of fossil quadrupeds had 

 been found in a superficial deposit of red sandy clay in this meadow; 



