94 Dr Daiibeny on the Volcanoes of Au*vergne, 
But it is time to take leave of speculations with which, how- 
ever scrupulously we resolve to adhere to simple deductions 
from facts, much hypothesis is necessarily blended, and proceed 
to another description of rocks found in the same neighbour- 
hood, previous to the account we mean to offer of the strata of 
IMount Dor, and of Cantal, with which the present paper will 
be concluded. 
On the Ancient Volcanic Rocks near Clermont. 
We are not to suppose, because the neighbourhood of Clei- 
mont is the principal seat of the more recent volcanoes, that no 
other rocks, referable to the same class, are therefore found about 
it. The Basalt of Montaudoux, which Dr Boue has remarked 
to be identical with the rock of Calder, between Glasgow and 
Edinburgh, evidently belongs to an era much more remote than 
that of the scoriaceous lava of Graveneire, to which it is so 
near. The mountain Gergovia, which we have already noticed 
as consisting, for the most part, of alternations of beds of the 
fresh-water formation, is capped, however, with a basalt, partly 
compact, and partly amygdaloidal, containing minute crystals 
of mesotype, pretty abundantly disseminated, which, of course, 
must be attributed to a period of time, anterior to the excava- 
tion of the valley which it overlooks.— At the Buy Marmont, 
near the Veyre, about three leagues south of Clermont, on the 
road to Brionde, I observed an alternation of that species of 
trap termed by the French Variolite, with limestone beds of the 
same description with the above. 
As this is a fact of some importance, and has not been noti-, 
ced by former travellers, I may be excused for dwelling a little 
upon it, in hopes of directing to the circumstance, the attention 
of geologists, who may correct my statement, in case of my ha- 
ving inadvertently fallen into any error in my description. 
The Buy Marmont, then, is capped with basalt, underneath 
which, is a calcareous rock, identical, both in its external cha- 
racters and imbedded petrifactions, with that of Gergovia. This 
is followed by a thick stratum, composed of a sort of tuff, contain- 
ing imbedded portions, not only of basalt and other trap-rocks, 
but even of limestone, and with occasional veins of the same 
substance. In the midst of this tuffaceous rock, rises a ridge, 
3 
