Dr Daubeny on the Volcanoes of Auvergne. 91 
ved hornblende rock, which appeared to graduate into the gra^ 
hite ; and these four rocks make up, as far as my observations 
extend, the higher portions of the mountain. On the lower, 
we have lavas, both compact and vesicular, none of which, so far 
as I observed, occupy the summit, although M. Montlosier, who 
examined the spot, doubtless with more attention, says he saw 
one small portion extending thus high. It should be remem- 
bered, that the Puy Chopine, even more distinctly than the Puy 
de Dome, is encircled by an amphitheatre of hills, which are 
comprehended under the names of the Puy Chaumont, and the 
Montagne des Gouttes. I examined these hills, and found 
them all to be volcanic, consisting chiefly of a tuff containing 
portions of scoria, and lavas of various denominations, all ce- 
mented together by an ochreous paste. Such, as far as I ob- 
served, appears to be the constitution of the Puy Chopine ; and 
the singular combination of rocks which it comprises, whilst it 
serves to explain its own formation, may, perhaps, furnish us 
with a clue to the theory of the Puy de Dome, and the other 
mountains similarly constituted. Encompassed on all sides by 
volcanic rocks, and bearing in themselves evidences of the agen- 
cy of heat, the igneous origin of these latter mountains will 
scarcely be disputed ; but it has been long a question, whether 
the Puy de Dome, and the other hills of a hke character, have 
merely been heated in their place, or whether they have been 
thrown up from below by the agency of a volcano, like some of 
the hills that have made their appearance in South America, or 
the Monte Nuova, near Vesuvius. 
M. D’Aubuisson seems to incline to the opinion, that the 
rock of the Puy de D6me,.&c. is only the relic of an extensive 
stream of lava, which probably covered a large tract on either 
side of it, but of which all the remaining portions, with the ex- 
ception of the five hills before alluded to, have since been 
swept away. Von Buch, on the contrary, whose opinion on 
such subjects is entitled to great weight, imagines that the 
mountains composed of domite have been thrown up from be- 
low, elaborated from the materials of the fundamental granite, 
altered partly by the effect of heat, and partly by elastic va- 
pours. The difficulty of supposing so complete a destruction 
of a stratum as is implied by M. D’Aubiiisson’s hypothesis, to- 
