^66 Dr Daubeiiy mi the Volcanoes of Aumrgne, 
rocks of Auvergne was first asserted and maintained, by an 
appeal to the structure of this particular mountain, who it is 
said accounted for the scoriae found on its surface, by gravely 
remarking that he had heard of iron-founderies haying former- 
ly been established on the spot. As we follow, however, what 
may be considered as the stream of lava derived from this 
mountain, by descending it on the side nearest Clermont, we 
observe the scoriaceous lava before described, associated with a 
basaltic rock of the most compact character, and approaching 
to a metallic appearance. It has imbedded fine crystals of augite 
and olivine, and bears in all respects a very strong resemblance 
to the rock of Arthur’s Seat, and some other of the Scotch 
basalts. 
If any doubts should arise as to the circumstances of two 
such different substances belonging to the same current, they 
will be removed when I remark that both are so intermixed, 
that portions of the scoriaceous are often seen in the midst of 
the compact lava; and masses of the latter surrounded by 
heaps of cinders, or with a cellular rock, which, both in com- 
position and external chai’acters, passes by imperceptible gra- 
dations into basalt. The association of a substance like this 
with undisputed lava, should render us cautious how we pro- 
nounce as to the origin of a rock from its external characters. 
If all basalts, to which an igneous origin is ascribed, owed their 
compactness to the . pressure they underwent, how is it that we 
see this very rock connected with a lava remarkable for its po- 
rous texture and vitreous appearance ? Or if we suppose pres- 
sure to have been in this instance applied to the compact va- 
riety, by what singular accident could the cellular lava have 
escaped that to which the other was subjected ? 
I mention these facts, rather with a view of inviting inquiry 
than of drawing any conclusion from them ; as in the case of 
the basalts and cellular lavas of Mont Dor, of which we shall 
afterwards speak, the position of the rocks was such, as tend- 
ed to confirm us in the idea of the difference in the two instan- 
ces having resulted from the degree of pressure, it is possible 
that those who may come after me may, by a more attentive 
examination of the Puy Graveneire, discover the reason for 
this apparent exception, consistently with the received notions 
on the subject. At the same time, I must remark, that the 
