Ch. XIX.] 
MINOR VOLCANOS OF AUVERGNE. 
263 
No. 56) is a conical mass, which has evidently been formed, 
like the cone of Etna, by a long series of eruptions. It is 
composed of trachytic and basaltic lavas, tufts, and conglo- 
merates, or breccias, forming a mountain several thousand feet 
in height. This volcano evidently broke out precisely on the 
site of the lacustrine deposit before described (Chapter xvii.), 
which had accumulated in a depression of a tract composed of 
micaceous schist. In the breccias, even to the very summit 
of the mountain, we find ejected masses of the fresh-water 
beds, and sometimes fragments of flint, containing Eocene 
shells. Deep valleys radiate in all directions from the central 
heights of the mountain, especially those of the Cer and Jour- 
danne, which are more than twenty miles in length, and lay open 
the geological structure of the mountain. No alternation 
of lavas with undisturbed Eocene strata have been observed, 
nor any tuffs containing fresh-water shells ; on the northern 
side of the Plomb du Cantal, at La Vissiere, near Murat, we 
have pointed out on the Map (wood-cut, p. 226) a spot where 
fresh-water limestone and marl are seen covered by a thickness 
of about 800 feet of volcanic rock. Shifts are here seen in the 
strata of limestone and marl *. 
Although it appears that the lavas of the Cantal are more 
recent than the fresh-water formation of that country, it does 
not follow that they may not belong to the Eocene period. 
The lake may possibly have been drained by the earthquakes 
which preceded or accompanied the first eruptions, but the 
Eocene animals and plants may have continued to exist for a 
long series of ages, while the cone 'went on increasing in 
dimensions. 
Train of minor Volcanos. — We shall next consider those 
minor volcanos before alluded to, which stretch in a long; range 
from Auvergne to the Vivarais, and which appear for the 
most part to be of newer origin than the mountains above 
described. They have been thrown up in a great number of 
isolated points, and much resemble those scattered over the 
* See Lyell and Murchison, Ana. des Sci. Nat., Oct. 1829. 
