VALLEY OF THE VEZEEE. 3 



strikingly evident at the same level on the two sides of the valley, where the 

 escarpments overlook the river, and where they are continued in the rocks 

 bordering the lateral valleys, down which small streams run into the Vezere. 

 Hence the first impression on the observer is that these are great lines of erosion, 

 due to the rapid movement and long-continued passage of a vast mass of water 

 that had filled both the principal and the accessory valleys. Further reflection, 

 however, and a more attentive examination soon suggest a more reasonable expla- 

 nation. 



When we approach the foot of these cliffs, it is readily seen that these masses 

 of rock, referable geologically to the Cretaceous Formation, present horizontal 

 beds of a somewhat various structure and composition. Some of the layers 

 are more susceptible than others of being attacked by the atmospheric agents 

 which degrade and eat into their exposed surfaces, whilst the harder intervening 

 layers resist better and remain as projections. Hence result the projecting ledges 

 and the long hollow linep, which, necessarily corresponding in level on the two 

 sides of the valley, suggest at first sight the action of water. 



Passing near these cliffs after a thaw, or even, in summer, at a time when 

 intense heat has followed moist and rainy weather, one may see both large thin 

 plates and small flakes and films of the rock scale off from the beds where the 

 hollow flutings are being formed ; and these scalings accumulate all along at the 

 foot of the escarpment, where they are sometimes reconstituted as solid masses by 

 the effect of calcareous infiltrations of the percolating waters. 



As for the upper cornices, the bed which supports them being continually 

 diminished by weathering, they project 

 horizontally sometimes far forward ; and 

 when by their weight they are forced 

 to break off, they fall and lie at the foot 



of the cliff, where some may be now T^k The cave, with bone., &c. 



observed that have been lying there for 

 centuries. 



It is thus possible to conceive that at- ^ *" ** bone8 ' *" 



mospheric Causes, however gently Operating, Diagram Profile of the Limestone Escarpment of 



may have powerfully contributed, in long Le Moustier, from the South-west, about 190 



. , . feet high. 



series of ages, to the widening 01 some 



valleys and this independently of the action of water, which indeed in many 



cases is limited to filling up the bottoms of the valleys. 



B2 



