THE GLACIAL PERIOD. 211 



He observed these in crossing the range by Ekaterinburg on his 

 way to the Obi. Just before reaching Ekaterinburg many 

 trainees of immense boulders running in parallel directions 

 were conspicuous, while farther east, on the shores of the Obi 

 (near to the mouth of the Irtysch), the superficial sands con- 

 tained in their lower portions many well-polished and striated 

 boulders. 1 



Still more remarkable, however, are the evidences of glacial 

 action in Western and South-western Europe. MM. Collenot 

 and J. Martin have shown that in the Morvan, near the sources 

 of the Seine, there is an abundant development of rock-striations, 

 striated stones, and erratics, which indicate the former presence 

 of very considerable nappes of ice. 2 Similar appearances show 

 themselves in the plateau of Central France. Not only have 

 many of the valleys of that region been filled with glaciers, but 

 extensive sheets of ice have overflowed the low grounds at the 

 base of the hills — scouring, striating, and polishing the rocks, 

 and covering them with a thick deposit of moraine profonde. 

 Large glaciers have descended from Mont Dore and the Puy de 

 Dome, and from the heights of Cantal, and their terminal and 

 lateral moraines are now conspicuous at the base of the moun- 

 tains and in such valleys as those of Allagnon, the Couze 

 d'Issoire, the Couze de Champeix, the Dordogne, etc. Traces of 

 the same nature occur in the neighbourhood of Clermont Ferrand, 

 which bespeak the former existence of several glaciers of the 

 second order, as in the valleys of the Auzon and of Eomagnat. 

 In short, it is evident that the great plateau of crystalline rocks 

 upon which are superposed the volcanic cones and masses of 

 Auvergne, has been covered with a mer de glace from which 

 glaciers protruded on all sides into the valleys. From the crests 

 of Forez and Mezeuc, and from the basaltic plateaus of Aubrac 

 and Vivarais, glaciers of more or less importance have descended. 3 



1 Nature, 1877, p. 306. 



2 Collenot : Bull. Soc. Geol. France, 2 e Ser. t. xxvi. p. 173 ; Jules Martin ; 

 Ibid., 2 e Ser. t. xxvii. p. 225. 



3 For old glaciers of Central France, see Ch. Martins : Comptes Bendus de 

 V Acad, des Sci. t. lxvii. p. 993 ; Quart Journ. Geol. Soc, vol. xxv. p. 46 ; Lecoq : 



