232 ELEMENTS OF GEOLOGY. 
tion either of the Parisian or English tertiary areas. For 
we are presented in Auvergne with the evidence of a series 
of events of astonishing magnitude and grandeur, by which 
the original form and features of the country have been 
greatly changed, yet never so far obliterated but that they 
may still, in part at least, be restored in imagination. Great 
lakes have disappeared—lofty mountains have been formed, 
by the reiterated emission of lava, preceded and followed by 
showers of sand and scoriae—deep valleys have been subse¬ 
quently furrowed out through masses of lacustrine and vol¬ 
canic origin—at a still later date, new cones have been 
thrown up in these valleys—new lakes have been formed by 
the damming up of rivers—and more than one assemblage 
of quadrupeds, birds, and plants. Eocene, Miocene, and Plio¬ 
cene, have followed in succession; yet the region has pre¬ 
served from first to last its geographical identity; and we 
can still recall to our thoughts its external condition and 
physical structure before these wonderful vicissitudes began, 
or while a part only of the whole had been completed. 
There was first a period when the spacious lakes, of which 
we still may trace the boundaries, lay at the foot of mount¬ 
ains of moderate elevation, unbroken by the bold peaks and 
precipices of Mont Dor, and unadorned by the picturesque 
outline of the Puy de Dome, or of the volcanic cones and cra¬ 
ters now covering the granitic platform. During this ear¬ 
lier scene of repose deltas were slowly formed ; beds of marl 
and sand, several hundred feet thick, deposited; siliceous and 
calcareous rocks precipitated from the waters of mineral 
springs; shells and insects imbedded, together with the re¬ 
mains of the crocodile and tortoise, the eggs and bones of 
water-birds, and the skeletons of quadrupeds, most of them 
of genera and species characteristic of the Miocene period. 
To this tranquil condition of the surface succeeded the era of 
volcanic eruptions, when the lakes were drained, and when 
the fertility of the mountainous district was probably'en¬ 
hanced by the igneous matter ejected from below, and pour¬ 
ed down upon the more sterile granite. During these erup¬ 
tions, which appear to have taken place towards the close of 
the Miocene epoch, and which continued during the Pliocene, 
various assemblages of quadrupeds successively inhabited the 
district, among which are found the genera mastodon, rhi¬ 
noceros, elephant, tapir, hippopotamus, together with the ox, 
various kinds of deer, the bear, hyaena, and many beasts of 
prey which ranged the forest or pastured on the plain, and 
were occasionally overtaken by a fall of burning cinders, or 
buried in flows of mud, such as accompany volcanic erup- 
