BONE- AND CAVE-DEPOSITS OF THE REINDEER-PERIOD. 163 



atmosphere. The bottom of the valley consists of an alluvial plain, varying in 

 width from to f of a mile, and skirted, first on one side and then on the other, 

 or occasionally on both, by a line of precipitous cliffs. In cases where the river 

 no longer flows at the foot of these cliffs, a considerable talus has been formed by 

 the weathering of the rock ; in some places the degradation has gone on to such 

 an extent that the side of the valley presents an even slope, though occasionally a 

 low cliff-like face of rock may be left exposed, as if to show that what is now for 

 the most part a uniform declivity may have been originally, when the river flowed 

 on that side of the valley, a sheer precipice. In other places, where the river now 

 flows at the foot of the cliffs, occasional masses of fallen rock, standing out from 

 the stream, which in many parts is very rapid in its course, testify to its under- 

 mining-power, though in one instance, at least, an ancient chateau, with the rock 

 on which it stands undercut to a great extent, but not yet brought down by the 

 river, proves that its action, though sure, is slow. Near Condat the river has 

 worked its way to a considerable depth beneath the level of its older alluvium, 

 and is gradually cutting away a low line of limestone cliff, some 15 or 20 feet in 

 height, and a full quarter of a mile away from the older boundary of the valley 

 at the margin of the alluvial plain. 



In hardly any case is the summit of the present line of cliffs at the highest level 

 of the surrounding country, but the cliffs form an abrupt termination to sloping 

 ground, on which beds containing large rolled pebbles of quartz, gneiss, mica- 

 schist, granite, and other of the metamorphic rocks of the country to the north- 

 east, through which the stream passes in the upper part of its course, are of 

 frequent occurrence. Whether these are in all cases connected with the beds of 

 Miocene age which cap a considerable portion of the plateau of the district, or 

 whether any of them represent the " high-level " gravels of the river, are ques- 

 tions which I will not attempt to determine. 



The height of the cliffs at the side of the valley must in many places be at least 

 300 feet ; and the scenery brought to view in descending the windings of the river 

 (as we did) in a boat, is strikingly picturesque. Owing to the different degrees of 

 hardness of different beds, which I have already mentioned, the weathering of the 

 face of the cliff has been very unequal. The percolation of water through the 

 softer beds, combined with the action of frost, has caused them to perish much 

 faster than harder beds above and below ; and the consequence has been that in 

 many (I may say most) places there are deep grooves along the face of the cliffs 

 following the almost horizontal lines of stratification, and where the cliffs stand 

 out like rounded bastions, following their contour. In some places two or three 



