320 PHASES OF ALPINE GLACIAL ACTION. 



Successive Phases of Glacial Action in the Alps, and their 

 Relation to the Human Period. 



According to the geological observations of M. Morlot, the 

 following successive phases in the development of ice-action 

 in the Alps are plainly recognisable : - 



1st. There was a period when the ice was in its greatest 

 excess, as described at p. 300 et seq., when the glacier of the 

 Rhone not only reached the Jura, but climbed to the height of 

 2,015 feet above the lake of Neufchatel, and 3,450 above the 

 sea, at which time the Alpine ice actually entered the French 

 territory at some points, penetrating by certain gorges, as 

 through the defile of the Fort de 1'Ecluse, among others. 



2nd. To this succeeded a prolonged retreat of the great 

 glaciers, when they evacuated not only the Jura and the low 

 country between that chain and the Alps, but retired some 

 way back into the Alpine valleys. M. Morlot supposes their 

 diminution in volume to have accompanied a general sub 

 sidence of the country, to the extent of at least 1,000 feet. 

 The geological formations of the 2nd period consist of 

 stratified masses of sand and gravel, called the ' ancient 

 alluvium ' by MM. Necker and Favre, corresponding to the 

 ( older or lower diluvium ' of some writers. Their origin is 

 evidently due to the action of rivers, swollen by the melting 

 of ice, by which the materials of parts of the old moraines 

 were rearranged and stratified, and left usually at considerable 

 heights above the level of the present valley plains. 



3rd. The glaciers again advanced and became of gigantic 

 dimensions, though they fell far short of those of the first 

 period. That of the Rhone, for example, did not again reach 

 the Jura, though it filled the lake of Geneva, and formed 

 enormous moraines on its borders, and in many parts of the 

 valley between the Alps and Jura. 



