20 Messrs Lyell and Murchison on the 



about 200 feet high, they must have left some marks of their 

 passage in that lava. But the rugged surface of the " cheire" 

 from the Etang de Fung to Mezayes, is remarkable for the en- 

 tire absence of sand or pebbles of any kind, or the slightest 

 covering of mud in the numerous hollows, as also for the an- 

 gularity of the blocks of loose scoriae scattered over it in abun- 

 dance. 



These last-mentioned circumstances tend also to invalidate 

 the conclusions of some geologists, who attribute powerful ef- 

 fects, in the shaping of hills and valleys, to mere frost, disin- 

 tegration, and the vertical descent of rain-water. It is at least 

 certain, that during the time required by the Sioule to excavate 

 the valley above described, no visible effect has been produced 

 on tlie exposed surface of the " cheire'" of Come. 



Volcano of Ckaluzet. 

 We shall next recall the attention of geologists to an inte- 

 resting spot near the village of Chakizet, on the Sioule, below 

 Pont Gibaud, where volcanic products were first noticed by 

 Dolomieu, and of which Mr Scrope has given a brief description 

 in his recent work. Previous to entering into details, it may be 

 desirable to give a slight sketch of the lava-current, and of the 

 source from whence it issued. 



. Immediately on the north of the village of Pranal rises a co- 

 nical hill called the Puy Rouge, composed entirely of red and 

 black scoria?, including much puzzuolana, and many volca- 

 nic bombs, which materials present about the same degree of 

 freshness of aspect as in the volcanoes of the Vivarais. On the 

 western side of this cone there is a considerable depression to- 

 wards the village of Chaluzet, resembling a worn-down crater, 

 and issuing from thence, a powerful stream of lava is to be tra- 

 ced round the western and southern sides of the Puy Rouge 

 by Pranal, until it almost entirely occupies the valley of the 

 Sioule, leaving only a narrow gorge through which that river 

 forces its passage. Hence the lava deflected to the north-west, 

 by the lofty and serrated ridge of gneiss which forms the right 

 bank of the Sioule, follows the course of that stream to Les 

 Combres, where it terminates. Throughout this space the 

 windings of the river arc so tortuous, that they must have ma- 



