The Glacial Theory of Prof. Agassiz. 361 



V, The interior valleys, and h^ the back of the chain, where some 

 of them are found. 



n, The lake of Neuchatel. 



g. The lake of Geneva. 



The difference of altitude between the Alps and Jura, distributed 

 over a space of fifty miles, gives an inclination of no more than two 

 degrees. Now, no current could force, or rather float, masses of stone, 

 weighing 1,000 tons, across an uneven valley of such breadth, although 

 the difference of level were much greater. Even if the valley had 

 then been filled up with gravel, or other solid materials, and formed a 

 regular inclined plane, as Ebel and Dolomieu assumed, the blocks could 

 not have been moved over it by water ; or, if moved, they would have 

 been rounded by attrition ; and, instead of being disposed in zones, 

 they would have been accumulated pel mel at the bottom of Jura. It 

 must be kept in mind, that the erratic blocks are found on the Italian 

 side of the Alps as well as the Swiss, and that currents and inclined 

 planes would be required in both directions. 



A more recent hypothesis, which assumes that the boulders were. 

 transported by icebergs when the great Swiss valley was under the sea, 

 is much more plausible. Agassiz objects to it, that it does not account 

 for the coat of sand and gravel covering the sides of the mountain on 

 which the large blocks generally rest, nor for the striated, grooved, and 

 polished surfaces, nor (he might have added) for the lapiaz and creux^ 

 and the lateral moraines which deviate from a horizontal position. 



It will be anticipated that Agassiz transports the boulders across the 

 great valley on a bridge of ice. He observes that the eastern Alps, as 

 they have disturbed the diluvium containing bones of elephants, must 

 have been raised up since that deposit was; formed, and their upheaval 

 is the last cataclysm, or geological convulsion, which has visited Europe. 

 Previous to this event, an immense mass of ice had covered the surface 

 of the northern parts of the old and new world ; " but when the up- 

 heaval of the Alps took place, this formation of ice was raised up like, 

 the other rocks ; that the fragments detached from the fissures of up- 

 heaval {fentes du soulevement) fell upon its surface, and without being 

 rounded — since they were not exposed to friction — moved along the in- 

 clined surface of the sheet of ice, in the same manner as the fragments 

 of rock which fall upon glaciers are carried to their sides in conse- 

 quence of the continual movement produced in the ice by its alternate 

 thawing and congelation, at the different hours of the day, and the dif- 

 ferent seasons. 



" After the upheaval of the Alps, the earth must have recovered a 

 higher temperature ; the ice in melting produced large funnels [enton^ 

 noirs) at the places where it was thinnest ; valleys of erosion were ex- 



Vol. xLii, No. 2.— Jan .-March, 1842. 46 



