354 PETRIFACTIONS AND THEIR TEACHINGS. CHAP. III. 



developing and determining the zoological characters and 

 relations of this highly interesting series of mammalian 

 remains. 



The country whence these fossils were obtained, and which 

 is the site of the extinct volcanoes, is about 220 miles south 

 of Paris, and forms a vast plain, situated in the department 

 of the Limagne d'Auvergne. It is so remarkable for its 

 fertility, that it is called the Garden of France ; a quality 

 attributable to the detritus of volcanic rocks which enters into 

 the composition of the soil. It is enclosed on the east and 

 west by two parallel ranges of gneiss and granite. Its average 

 breadth is twenty miles, its length between forty and fifty, 

 and its altitude about 1,200 feet above the level of the sea.' 

 The immediate subsoil of this plain is formed of alluvial 

 deposits composed of granitic and basaltic pebbles and 

 boulders, spread over beds of freshwater limestone. 



Hills of various elevations are scattered over the plain ; 

 and the river Allier flows through the district over strata of 

 limestone, marl, and sandstone, except where it has excavated 

 a channel through these sedimentary beds to the foundation 

 rock of granite. The calcareous deposits are the remains of a 1 

 .formation which once constituted an ancient plain of a higher 

 elevation than the present tract ; many of these hills are capped 

 by a crest of basalt, to which their preservation is in great 

 measure owing ; others have escaped destruction in conse- 

 quence of the durable and hard nature of the limestone of 

 which they are composed. 



Thus we have as the ground plan of the district, an exten- 

 sive plain, checquered with low hills of fresh-water limestone, 

 that are capped with compact lava j l the boundaries of this 

 tract being a range of primary rocks, 3,000 feet high. To the 

 westward the limestone disappears, and a plateau of granite 

 rises to a height of 1,600 feet above the valley of Clermont, 

 being 3,000 feet above the level of the sea. This elevated tract- 

 supports a chain of volcanic cones and dome-shaped mountains, 2 

 about seventy in number, which vary in altitude from 100 to j 

 500 feet above their bases, and form an irregular range of ,' 



1 I would refer the reader to " Wonders of Geology," p. 268, for a more 

 particular account of these phenomena; the classical works on the 

 geology of Auvergne are therein pointed out. 



> Ibid. PI. II. ^ 





