82 M. Oh. Martins on (he 



the high valleys of the Alps, while the terminal escarpment 

 rested on the Jura. In like manner, on the southern decli- 

 vity of the chain, the glaciers descended into the plains of 

 Piedmont and Lombardy. Those of the southern side of Mont 

 Blanc united to form the glacier of the Val d'Aoste. Its ter- 

 minal moraine rose like' a gigantic mound in the neighbour- 

 hood of the town of Yvree ; it is the Serra of Piedmont. The 

 greater part of the lakes of Upper Italy owe their existence 

 to the frontal moraines of these great glaciers ; by obstruct- 

 ing the course of the rivers, they have forced them to extend 

 themselves in the form of liquid sheets. Among the most 

 evident moraines, I may mention the three concentric arcs 

 which bound the extremity of the Lago Maggiore, near Ses- 

 to-Calende ; those of the Lake Garda are not less distinctly 

 characterised, in the environs of Desenzano and Peschiera. 



6. Of the Climate of the Glacial Epoch. 



When the imagination conceives all the countries which 

 surround the Alps buried under the ice to the distance of 

 many leagues, it trembles, so to speak, at the idea of the 

 dreadful cold which must result from this prodigious de- 

 velopment of the Alpine glaciers. It would seem that the 

 climate of Siberia presents nothing sufficiently rigorous to 

 explain the permanent existence of this mantle of ice extend- 

 ed over countries which now enjoy a temperate climate. It 

 is easy to shew that these notions are exaggerated. 



In fact, what we have said respecting the transformation 

 of snow into ice by repeated meltings and congelations, must 

 lead us to understand that there could not be glaciers with a 

 climate of extreme severity, such as that in the north of Si- 

 beria. Spitzbergen, which realises in the highest degree the 

 conception of a country enveloped in glaciers, since they de- 

 scend in all directions even to the sea, has a mean tempera- 

 ture of 8 centigrade degrees below zero ; that of summer, is 

 2°*4 above it. Iceland, where the glaciers rest on the shores 

 of the sea, but never pass beyond them, like those of Spitz- 

 bergen, presents, at different points, a mean temperature com- 

 prised between zero and + 4°. We could form an idea, by 

 means of a very simple calculation, of the climate which 

 would bring the glaciers of Mont Blanc to the margin of the 



