110 LITERATURE ON TORRENTS. 



And in view of the whole he (M. C6zanne) is led to conclude that this 

 which he is disposed to designate the torrential geological era must have 

 been immediately posterior to what is known as the glacial period. To 

 the consideration of the phenomena illustrative of this point, and of pheno- 

 mena occurring during the alleged era, is devoted the penultimate chapter 

 of the work. 



More immediately connected with the subject of rehoisement is the 

 following resume given by him of the whole series of phenomena brought 

 under review : — 



" There may be given in a few words a risumi of the whole series of 

 these phenomena. 



" The mountains are the result of a series of upheavals following one 

 upon another in the same region. A final agitation gave to the different 

 chains of these the existing elevation ; it elevated the summit and opened 

 up deep fissures or divisions, which have become the valleys of the present 

 time. From the time this occurred the waters began to fashion the thalwegs, 

 following the line which best suited them ; wearing down outlets and filling 

 up basins. It is necessary to admit, or to assume, that the depth or thick- 

 ness of the alluvial deposits in the bottom of certain valleys — for instance, 

 those of the Isfere in the Graisivaudan, or of the Khine in Alsace, — is to be 

 reckoned by hundreds, and perhaps by thousands, of mfetres or yards ; for 

 even yet certain lakes existing in depressions of the Alps have their bottom 

 below the level of the sea. 



" After a long series of ages the mountains assumed the leading features 

 which they now exhibit, when, the climate changing, great glaciers carried 

 on actively the work of erosion ; these have planed away escarpments, 

 and fashioned into something like horizontal lines the rocky belts of 

 the valleys. 



" Dehdcles, or inundations, from the escape of the waters of pent-up lakes, 

 and deluges resulting from the tremendous rains of summers on the 

 extensive fields of ice, have carried away and deposited in the principal 

 valleys in certain favourable places, but more especially at the debouchicres 

 of lateral gorges, the masses of loess which have formed cones in the higher 

 plains, and in which the water-courses have subsequently dug out the 

 secondary valleys. 



" At a later period, after the melting away of those glaciers, the torrents 

 seized upon the bared mountains ; and without restraint they have dug out 

 their basins, and have again taken up the materials disintegrated by the 

 glaciers, and deposited these in the gigantic cones which give to certain 

 regions a physiognomy peculiarly their own. 



" But after a time the forests, spreading by degrees, stifled the waters 

 under a mantle of verdure ; the torrents became extinct, — an era of peace 

 and of comparative quiet supervened in the mountains ; then the tribes of 

 men, who during the glacial period rambled over the low-lying plains, in 

 company with the reindeer, the aurochs, and the bears, began to spread 

 themselves in the high-lying valleys. The most ancient settlements were 

 made at the gorges of the torrents, towards the summit of the cone ; in 

 point of fact, there are to be found in the mountain valleys very few of 

 these gorges in which we do not meet either with an existing village or 

 with an ancient ruin. 



" In this location, which was then one favourable to their pursuits, the 

 primary inhabitants could profit by the exceptional fei-tility of the cone of 



