AMONG THE VOLCANOS AND GLACIERS OF AUVERGNE. 15 
sides of a lovely wooded glen — sentinels to the approach to the 
old volcano. They consist of columnar phonolite, and it is 
impossible to describe the beauty of the shaft-like columns of 
Tuiliere. Some of the columns are curved, and slates are 
quarried at Tuiliere in cleavage planes, which are at right 
angles to the axis of the columns. We remarked, too, the 
inter-bedding of yellowish, soft, trachytic ash, with beds of 
hard basalt on Puy Gros. This soft trachyte weathers out 
easily, and its consequent denudation is the cause of the beautiful 
valley scenery we drive along en route to Mont Dore les Bains. 
Lake Guery, which is passed on the right, is famous for its 
red-fleshed trout, and the lake itself is walled in by basalt from 
the Puy Gros. It is from the Puy de FAiguiller, on the 
north, that the great lava current has issued which stretches 
for a distance of fifteen or sixteen miles along the banks of the 
Sioule river, and covers the granitic plateau at Pont Gibaud. 
Those who visit Pont Gibaud from Clermont may thus gain 
some idea of the extension of the ancient lava currents of 
Mont Dore. 
It is impossible to give a better description of Mont Dore 
than that of Scrope, viz., a great volcanic mountain like 
Etna or Teneriffe, which has been reduced to a mere skeleton 
by the wear and tear of long ages of denudation ; and no geo- 
logist can cross its peaks and cols, traverse its lava currents, 
explore its valleys all round the base, as we have done, without 
seeing how the upper and softer materials of the volcano have 
been swept away to form conglomerates and breccias, which 
have been carried for miles, and the very innermost dykes and 
porphyritic masses of the inner structure have been laid bare. 
With regard to the volcanic structure of Mont Dore the 
phenomena are far too vast and varied to be treated of here ; 
but we may say that a steady examination of the valley of the 
Dordogne on one side, and the valley of Chambon on the other, 
will go far towards giving the physical geologist a good idea of 
its history. Scrope’s section of the Cascade du Mont Dore, 
with its succession of soft trachytes, interlaced with hard lavas 
and basalts, is a good lesson in volcanic structure ; while the 
study of the valley of the Dordogne from side to side, and the 
evidence that it has once been filled with volcanic materials 
to the level of the upper basalt, and has since been eroded to 
the depth of 800 ft., is a lesson on the denudation and erosion 
of the other valleys. 
We visited Mont Dore in May, 1876, for the purpose of 
examining into the evidence of glacial action, and the former 
existence of ancient glaciers in Central France, suggested by 
Dr. Hooker, of Kew, in a contribution to “ Nature,” of Nov. 11, 
1875. The glacial appearances due to weathering among the 
