22 THEORY OF THE -EARTH. 



Here, therefore, we have a collection of facts, a 

 series of epochs, anterior to the present time, of 



that they could only have been produced by enormous 

 eruptions. De Buch and Escher have recently em- 

 ployed themselves upon this subject. The memoir of the 

 latter, inserted in the Nouvelle Alpina of Steinmiiller, 

 vol. i. presents the general results in a remarkable man- 

 ner. The following is a comprehensive view of them : 

 Such of these blocks as are scattered over the low parts of 

 Switzerland and Lombardy, come from the Alps, and have 

 descended along their valleys. They occur every where, and 

 of all sizes, up to 50,000 cubic feet, over the great extent of 

 country which separates the Alps from the Jura mountains ; 

 and they rise upon the sides of the latter facing the Alps, 

 to a height of 4000 feet above the level of the sea. They 

 are found at the surface, or in the superficial layers of debris, 

 but not in the strata of sandstone, molasse, or conglomerate, 

 which fill up almost every where the interval in question. 

 They are sometimes isolated, sometimes in heaps. The 

 height of their situation is not connected with their magni- 

 tude ; the smaller ones alone appear sometimes a little worn, 

 but the large ones are not so at all. Those which belong to 

 the basin of each river are found, upon examination, to be of 

 the same nature as the mountains of the tops or sides of the 

 high valleys in which the tributary streams of this river 

 take their rise. They are already seen in these upper val- 

 leys, and are particularly accumulated at the places which 

 are situated above some of the contractions of these valleys. 

 They have passed over the lower hills, when their height has 

 not been more than 4000 feet ; and then they are seen upon 

 the other side of the ridges, in the cantons between the Alps 

 and Jura, and even upon the latter itself. It is opposite the 

 mouths of the valleys of the Alps that they are seen in the 



