Dr Daubeny on the Volcanoes qf Auvergne. 365 
ly ran parallel to each other, in a direction from north to 
south, and entered the plain of Pont Gibaud by two defiles, 
separated by the intervention of two hills. But one branch of 
the lava of Come has so obstructed the course of the river 
Menges, that the waters have been directed to the east, where 
they have worked themselves a passage through an argillaceous 
hill ; made immense excavations in it, and have thus reached 
the bed of the river Sioule, a league and a half higher up than 
-ithey would naturally have done. Compelled, however, to flow^ 
in a direction contrary to the slope of the country, a large por- 
tion of the waters constantly stagnates in its channel, and has 
formed a swamp, which goes by the name of the Etang de 
Fung.” A portion only of the stream flows by the original 
outlet, which, it seems, was not completely obstructed by the 
torrent of lava. The rest accumulates in the pool of Fung, un- 
til the waters have risen to a height ' sufficient to drain off by 
the channel, communicating with the river Sioule, which they 
have made themselves to the east. 
A somewhat similar circumstance has happened to the Lake 
Aidat, which is obstructed by a stream of lava, that may be 
traced from the Puy de la Vache, a mountain at least a league 
distant. 
In this case, however, a still greater impediment existing to 
the escape of the waters by any other outlet, the obstacle has 
merely had the effect of raising the level of the lake, which 
has at length succeeded in cutting itself channels through the 
parapet of lava thrown across it, the projecting portions of 
which appear like islands in the midst. 
With reference, however, to the more immediate objects of 
my inquiry, I know of none of the hills in the neighbourhood 
of Clermont which interested me more than the Puy Gra- 
veneire. This mountain, which lies within two miles of Cler- 
mont, seems, as we approach its summit, to consist of an entire 
mass of cinders so that we may in some degree comprehend 
the origin of the ludicrous opinion ascribed to a professor of 
the Academy of Clermont, when the volcanic nature of the 
In descending it, however, to the west, we find that the rock subjacent is 
granite, which exhibits marks of dislocation. 
VOL. IIT. NO. 6. OCTOBER 1820 . B b 
