320 PHASES OF ALPINE GLACIAL ACTION. chap. XV. 



Successive Phases of Glacial Action in the Alps, and their 

 Melation 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 recognizable: — 



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 

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

 2015 feet above the Lake of JS^eufchatel, and 3450 above the 

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

 territor}' at some points, penetrating by certain gorges, as 

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



2d. 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 retii*ed 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 1000 feet. 

 The geological formations of the 2d 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 hy the melting of ice, by 

 which the materials of j^arts of the old moraines were re- 

 arranged and stratified, and left usually at considerable 

 heights above the level of the present valley-plains. 



3d. The glaciers again advanced and became of gigantic 

 dimensions, though the}^ fell far short of those of the first 

 period. That of the Ehone, 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 

 vallc}' between the Alps and Jura. 



