210 On the Antiquity of the Volcanos of Auvergne.  [April, | 
before us the general Physiognomy of the country, so as better to 
enable us to realize the force of the evidence he had brought forward. 
To this work, and to the memoir of Lyell and Murchison, ‘On 
the Excavation of Valleys, as illustrated by the Volcanic Rocks of 
Central France,’ I am chiefly indebted for the few facts the space 
allotted me admits of my bringing forward in proof of the great 
antiquity even of the more modern class of eruptions. 
Let us take the case of the volcano of Chaluzet, near the village 
of Pont Gibaud. 
This is a conical hill, composed of red and black scorie, having 
on its summit a depression resembling a worn-down crater, from 
which may be traced a powerful stream of lava descending into the 
valley below, in which the river Sioule flows. Deflected to the 
north-west by the lofty and serrated ridge of gneiss which forms 
the right bank of the stream, the lava-current follows its course as 
far as “ Les Combres,” where it terminates. 
The upper portion of the mass is scoriaceous, the lower compact 
and prismatic, and the under-surface of the prisms stands at a,height 
of about 50 feet above the present bed of the Sioule, resting upon a 
bed of pebbles. 
The pebbles have indeed been traced some way into the rock, in 
consequence of a gallery driven in horizontally through the upper 
part of the gneiss and the interposed alluvium, so as to render it 
clear that the lava-stream really rests upon the latter. 
FIGs: 
uly 
(il —240° 
i 
en 
Vf 
UT ati ll 
> hos = ff Yi, 
il 
== Z> 
TT O//// 
Lilla WY); L, 
A. Scoriaceous Lava, B. Columnar Basalt. GC. Bed of Pebbles. 
D. Gneiss. E. Path. G. River Sioule. 
