32 Messrs Lyell and Murchison on the 



would have occurred to us, had not our attention been chiefly 

 directed to the relations and characters of the tertiary strata *. 



Mr Scrope has mentionedt, that, in following the course of 

 the lava of Tartaret, the sides of the valley are seen fringed at 

 higher elevations, by sections of more ancient currents which 

 have flowed in the same direction. We were enabled to con- 

 firm his inferences from these facts, by finding under one of 

 these remnants of more ancient basalt a pebble-bed resting on 

 granite, and containing granitic sand and gravel, with some few 

 boulders of basalt, probably referable to one of the ancient ba- 

 saltic plateaus. This section is seen on descending the hill to 

 the town of Champheix, by the road from St Saturnin, on the 



• Many authors have cited localities in Central France, where basaltic 

 plateaus at different, and often very considerable, elevations above the pre- 

 sent valleys, repose on alluvions. Among these, we may enumerate, in the 

 order of date of their works, Messieurs Le Grand d'Aussi, Montlosier, Ra- 

 mond, Scrope, and Bertrand Roux. We examined, in company with the last 

 mentioned gentleman, several examples near Puy en "Velay, and had so many 

 opportunities of attesting the fidelity of all his geological observations, that 

 we confidently rely on numerous other cases cited in his work, and we refer 

 the geologist to them. 



Since the present memoir was written, Messrs Croizet and Jobert have 

 published the first part of their great work on the Fossil Bones of the De- 

 partment of the Puy de Dome, in which they notice some important cases of 

 alluvions beneatli basaltic coulees of different epochs. Of the most ancient 

 class observed by them, is the alluvion under Puy Solignat, south-west of Is- 

 soire, on the right bank of the Couze, and facing Mont Perrier. Here the 

 gravel bed beneath the old basalt is upwards of 2000 feet above the level of 

 the sea, and the pebbles consist of the primary rocks of the immediate neigh- 

 bourhood and of the tertiary formations ; and, as no basalt is found in this de- 

 tritus, it is inferred, that, when these alluvions were deposited on the tertiary 

 strata, few or none of the oldest volcanoes had then burst out.— P. 76. 



Of the next in age of these pebble-beds, a good example is seen under one 

 jjortion of the basaltic plateau of Pardines, where the detritus contains some 

 portions of old compact basalt, vvhich, it is inferred, has been derived from the 

 loftier coulees of the same epoch, as that of Solignat. The third period com- 

 prehends the alluvial beds, containing the bones of many extinct quadrupeds, 

 at Mont Perrier, Boulade, &c., where they are overlaid by, and alternate 

 with, mountainous masses of ti'achytic breccia. A fourth class of gravel beds 

 are seen under the la v^a- currents which have issued from the most recent vol- 

 canic vents, and in these the bones of elephants and other animals are found. 

 Lastly, they describe the superficial gravel and sand in the present valleys 

 and river beds. 



t Geology of Central France, p. 117. 



