6 
POPULAR SCIENCE REVIEW. 
near Clermont we recommend the walk through the village of 
Chamalieres to Eoyat. The church of Eoyat is old and sin- 
gular, and exhibits portions of early Eomanesque architecture, 
and the village and valley are extremely picturesque. The 
lava which has been poured down from Graveneire into the 
valley is well displayed in a fine section near the 66 grotto,” 
and a walk up the stream will afford a good idea of the. 
excavations through the lava effected by the rivulet. Oppo- 
site Eoyat there is a quarry called the “Carrieres Blanches,”' 
where a felstone porphyry is injected into the granitic rocks of 
Villar, and, protruding at the surface, forms a boss. Here we 
found growing, in May last, a large purple Iris, with Anemone 
montana ; and many swallow-tail butterflies were chasing each 
other in the sunshine round the knoll. From thence we pursue 
the route to the hill of Graveneire . There is no crater ; but 
immense masses of red and black scoriae, lapilli, and pozzuolana, 
quarried for their materials, look as if they had been ejected 
yesterday, and tell the tale of igneous action as would a black- 
smith’s forge. The volcanic masses appear to have been erupted 
through fissures in the granite hill known as the Puy de 
Charade , and three streams of lava flowed down the slopes. 
Besides the Eoyat lava stream on the north, two streams flow 
towards the east and south. The eastern current was turned 
aside out of its course by the Puy de Montaudoux , a rock of 
basalt of far more ancient date, and which occupied its present 
position for untold ages before the volcanic outbursts of Gra- 
veneire had commenced. From Graveneire we recommend the 
walk to the Puy de Berze. 
The Puy de Berze is more than 3,000 ft. above the sea, and 
its summit is capped by basalt overlying granite. We here 
remark the difference of position of this old lava as compared 
with that of the valley of Eoyat. Mr. Scrope thought that the 
basaltic currents which overflowed the freshwater beds of Ger- 
govia, and the isolated Montrognon which forms so striking a 
feature in the scenery of Clermont, had their source in an 
aperture near the summit of Berze, and flowed downwards into 
the lake, overflowing the lacustrine silts and their shells, where 
now stand Gergovia and Montrognon. Again, at St. Genest, 
there is a little valley with a rivulet into which has been poured 
a stream of columnar basalt with veins of quartz ; and we see 
that the granitic mass had been here eroded before the outflow 
of the basalt. On the road to Montrognon and Clermont the 
granitic rocks are much disintegrated by the action of the at- 
mosphere, and present appearances which might easily be set 
down as due to ice action. The rocks here and there by the 
roadside look as if they were moutonnees by ice; while the 
granitic masses separating at the joints form rounded boulders. 
