363 The Glacial Theory of Prof. Agassiz. 



cavated at the bottom of these openings, in localities where no current 

 could exist unless enclosed between walls of ice ; and, when the ice 

 disappeared, the large angular blocks were found resting on a bed of 

 rounded pebbles, of which the smallest, often passing into a fine sand, 

 form the base." 



The description of the supposed phenomena attending the upheaval 

 of the Alps, though it forms the very kernel of his theory, is less clear 

 than the other parts of M. Agassiz's work, which is generally very per- 

 spicuous ; and instead, therefore, of giving the substance of his state- 

 ments in our own language, we have translated the two most important 

 passages literally. In a paper read before the Helvetic Society of Nat- 

 ural History in 1837, containing the germs of the theory, more fully 

 unfolded in his new work, he thus expresses himself: — 



" The appearance of the Alps, the result of the greatest convulsion 

 which has modified the surface of our globe, found its surface covered 

 with ice, at least from the North Pole to the shores of the Mediterranean 

 and Caspian Seas. This upheaving, by raising, breaking, and cleaving 

 in a thousand ways, the rocks which compose the prodigious mass that 

 now forms the Alps, at the same time necessarily raised the ice which 

 covered them ; and the debris detached from so many deep upbreak- 

 ings and ruptures, naturally spreading themselves over the inclined sur- 

 face of the mass of ice which had been supported by them, slid along 

 the declivity to the spots lohere they were arrested, without being worn 

 or rounded, since they experienced no friction against each other, and, 

 even when arrested, came in contact with a surface so smooth ; or, af- 

 ter being stopped, they were conveyed to the margin or to the clefts of 

 this immense sheet of ice, by that action and those movements which 

 characterize congealed water when it is subjected to changes of tem- 

 perature, in the same manner as the blocks of rock which fall upon 

 glaciers, approach their edges in consequence of the continual move- 

 ments which the ice experiences, in alternately melting and congealing 

 at the difl^erent hours of the day and seasons of the year." — Edinburgh 

 New Philosophical Journal, No. 48, p. 378. 



The words in italics indicate an opinion that some of the boulders 

 might have slid from the Alps to Jura on the surface of the ice, 

 while others adhered to it, and only travelled as the angular blocks 

 resting on glaciers now travel. Nothing equivalent to these words oc- 

 curs in the Etudes, and even the distribution of the fragments by the 

 more tardy process is not very clearly explained. We are not sure, 

 for instance, whether he means that the ancient mer de glace rose above 

 Jura, and determined the progressive motion of the ice in a direction 

 away from the Alpine chain at right angles, bearing the boulders first 

 detached over Jura into the basin of the Doubs, and that, owing to the 



