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Show 256 EOCENE PERIOD. [Ch. XVIII. googrnhp yof tl)e northern hemisphere was. very distinct. Oul' . b'l't t account for the atmospheric and other latent ma 11 y o · 'd · causes, w In ·c h of ten give rise to the mos·t destru. ct1 vc ep1 cmics, proves t h e ex tent of our iOb 'noran• cc of the cnt1re assembl.a ge of con d1. t1· ons 1· equ1's1'te for the existence of any one spec1es on the globe. CHAPTER XIX. Volcanic rocks of the Eocene period-Auvcrgne-Igneous formations associateu with lacustrine strata-Hill of Gergovia-Eruptions in Central France at sue• cessive periods-Mont Dor au extinct volcano-Velay-Plomb du CantnlTrain of minor volcanos stretching fwm Auvergne to the Vivarais-Monts Domes-Puy de Come-Puy Houge-Raviues excavat~d through lava-Currents of lava at different heights-Subjacent alluviums of distinct ages-The more modern lavas of Central France may belong to the Miocene pm·iod-The integ1·ity of the cones not inconsistent with this opinion-No ernptions during the historical era-Division of volcanos into ante-diluvian and post-diluvian inadmissible- Theories respecting the effects of the l<'lood considered-Hypothesis of a partial flood-Of a universal deluge-Theory of Dr. Buckland as controverted by Dr. Fleming-Recapitulation. EOCENE VOLCANIC ROCKS. WnEN we tt·cated in the seventeenth chapter of the lacustrine deposits of Central France, we purposely omitted to give a detailed account of the associated volcanic rocks, to which we now recall the attention of the reader. (See the Map, p. 226.) '\iV e stated that, in the arenaceous ann pebbly group of the lacustrine basins of Auvergne, Can tal, and Velay, no volcanic pebbles had ever been detected, although massive piles of igneous rocks arc now found in the immediate vicinity. As this observation has been confirmed by minute research, we are warranted in inferring, as we before explained, that the volcanic eruptions had not commenced when the older subdivisions of the fresh-water groups originated. In Cantal and Velay we believe no decisive proofs have yet been brought to light that any of the igneous out-bursts happened during the deposition of the fresh-water strata; but there can be no doubt that in Auvergne some volcanic explosions took place before the drainage of the lakes, and at a time when the Eocene species of animals and plants still flourished. We shall first advert to these proofs as relating to the history VoL. III. S |