Ch. XXXIL] 



TERTIARY VOLCANIC ROCKS. 



547 



Fig. 6T6. 



Section from the vallej'- of the Couze at Nechers, through Mont Perrier and Issoire to the Vallej 

 of the Allier, and the Tour de Boulade, Auvergne, 



10. Lava-current of Tartarct near its termina- 

 tion at Nechers. 



9. Bone-bed, red sandy clay under the lava of 

 Tartaret. 



8. Bonehed of the Tour de Boulade. 



7. Alluvium newer than No. 6. 



6. Alluvium with bones of hippopotamus. 



5 c. Trachytic breccia resembling 5 a. 



5 h. tipper bone-bed of Perrier, gravel, &c. 



5 a. Pumiceous breccia and conglomerate, angu- 

 lar masses of trachyte, quartz, pebbles, &c. 



5. Lower bone-bed of Perrier, ochreous sand 



and gravel. 

 4 a. Basaltic dyke. 

 4. Basaltic platform. 

 3. Upper fresh-water beds, limestone, marl, 



gypsum, i'c. 

 2. Lower fresh-water formatico, red clay, green 



sand, &c. 

 1. Granite. 



may convey some idea to the reader of the long and . omplicated series 

 of events which have occurred in that country, since the first iacustrine 

 strata (No. 2) were deposited on the granite (No. 1). The changes of 

 which we have evidence are the more striking, because they imply great 

 denudation, without there being any proofs of the intervention of the 

 sea during the whole period. It will be seen that the upper fresh-water 

 beds (No. 3 j, once formed in a lake, must have suffered great destruc- 

 tion before the excavation of the valleys of the Couze and Allier had 

 begun. In these fresh-water beds, Upper Eocene fossils, as described 

 in Chap. XV., have been found. The basaltic dike 4' is one of many 

 examples of the intrusion of volcanic matter through the Eocene fresh- 

 water beds, and may have been of Upper Eocene or Miocene date, giv- 

 ing rise, when it reached the surface and overflowed, to such platforms 

 of basalt, as often cap the tertiary hills in Auvergne, and one of which 

 (4) is seen on Mont Perrier. 



It not unfrequently happens that beds of gravel containiug bones of 

 extinct mammalia are detected under these very ancient sheets of basalt, 

 as between No. 4 and the fresh-water strata, No. 3, at A, from which it 

 is clear that the surface of No. 3 formed at that period the lowest level at 

 which the waters then draining the country flowed. Next in age to this 

 basaltic platform comes a patch of ochreous sand and gravel (No. 5), 

 containing many bones of quadrupeds. Upon this rests a pumiceous 

 breccia or conglomerate, with angular masses of trachyte, and some 

 quartz pebbles. This deposit is followed by 5 h, which is similar to 5, 

 and 5 c similar to the trachytic breccia 5 a. These two breccias are 

 supposed, from their similarity to others found on Mount Dor, to have 

 descended from the flanks of that mountain during eruptions ; and the 

 interstratified alluvial deposits contain the remains of mastodon, rhino- 

 ceros, tapir, deer, beaver, and quadrupeds of other genera referable to 

 about forty species, all of which are extinct. I formerly supposed them 

 to belong to the same era as the Miocene faluns of Tourainej but, 



