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UNDESCRIBED CRATER OF FIOLLONGE—SINGULAR FLUIDITY OF LAVA. 31 
tinued longer than I expected, as we scrambled with some difficulty along the 
bank of the river. I carefully marked here, as elsewhere, every patch of lava 
upon Cassius map. The disappearance of the lava in this place is no doubt 
due to the steepness and narrowness of the channel, which left few points of 
lodgment for the lava, and which gave an increased force to the eroding power 
of water. 
We passed successively the hamlets of Lespereyres and Chabron; and after 
the last we kept in the hollow of the valley, arid soon got a sight of a great lava 
cliff, betokening our approach to the crater. Clambering high above the left 
bank of the stream (which we crossed above Chabron) to avoid precipices, we at 
length, after a fatiguing walk of three hours from Burzet, obtained a view of a 
very remarkable cascade, which descends from near the crater which formed the 
object of our search, which, from a cottage occupying its centre, I called the 
Crater of Fiollonge. The cascade is called Raipis; and the water falls by several 
steps over a mass of beautifully columnar lava several hundred feet high. These 
interesting objects more than rewarded our perseverance. They are described, 
so far as I am aware, by no previous writer, and were probably seen by a geolo- 
gist then for the first time. Plate VI., fig. 4, gives a view of the cascade. 
The crater presents, as usual, an insulated cone of scorie, touching the 
granite in its whole circumference, except on the side next the valley, where a 
flood of lava has made its escape, damming the lateral stream, and forming the 
great cascade. In the slag adjoining the cascade are immense masses of im- 
bedded granite; which give additional countenance to the notion of the meta- 
morphic origin of the olivine nodules which so remarkably characterize this lava 
in all its extent. The columnar formation at the cascade, though far from the 
most extensive, is probably the most curious and complex in its forms of aggre- 
gation of any in the Vivarais. 
If we now consider the operations of this volcano, we shall find the ae 
length of its lava-produce to be really surprising. Although, by the map, the 
distance of the crater from Burzet may not appear to be more than 4 or 5 miles, 
the contortions of the bed of the stream are such, that it is probably double that 
distance ; and, indeed, can hardly be less than 8 miles, since we were 3 hours 
on the way (steep and rough as it was). To the junction with the lava of the 
Gravenne, in the valley of Montpezat, is therefore more than 12 miles; and if 
it be the same lava (as Mr Scrope supposes, and as there is some reason to 
think) which continues to the Pont de la Beaume, the distance will be 16 miles. 
Yet the whole valley of Burzet is a ravine so narrow and crooked, that the lava 
appears like a thread winding through it; and we are amazed that it should not 
have become solidified by the contact with the cold granite, before it had per- 
formed one-fourth of the distance. I apprehend that there is no lava known, 
ancient or modern, which has formed so attenuated a stream. This is only to be 
accounted for by its excessive fluidity, of which we have additional evidence, (1.) 
