383 



forms us is merely a development of one first advanced by M. 

 Venetz. The Alpine blocks, according to these writers, were not 

 carried by water, for had that been the case the largest would 

 be either in the Alpine valleys or near the base of the great chain, 

 and we should find their size and number diminish as we receded 

 from their original point of departure. But the fact is otherwise, 

 many of the blocks on the Jura, or those farthest removed from 

 the starting-place, being of the largest dimensions. They suppose, 

 therefore, in accordance with the opinion of M. de Beaumont and 

 others, that the elevation of the Alps occurred at a comparatively 

 modern epoch, and that when these mountains were first upheaved 

 they were more lofty than now, and more deeply covered with snow 

 and glaciers. After the principal movement had ceased, a lower- 

 ing of the Alps took place, the dislocated and shattered beds re- 

 quiring time to settle down into their present more solid and stable 

 form. According to this hypothesis, therefore, the erratic blocks 

 are monuments of the greater magnitude and extent of the ancient 

 glaciers under a different configuration of the surface. I have not 

 space for all the ingenious arguments adduced, after a minute exa- 

 mination of the ground by M. Charpentier in support of this theory, 

 but must refer you to the original memoir *. 



Before leaving this subject I may observe, that although it is rare, 

 in modern times, to meet with icebergs in the northern hemisphere 

 so far south as the Azores, in north latitude 42°, yet they have been 

 seen there, and not unfrequently in north lat. 44°, within the pre- 

 sent century, thus reaching the parallel of Southern Italy and Cen- 

 tral Spain. In the southern hemisphere we learn from Capt. Hors- 

 burgh that some large ones were carried, in 1828, still nearer to 

 the equator as far as lat. 35° south, or within about forty miles of 

 the Cape of Good Hope. I do not remember, when examining 

 alluvial deposits, to have seen any blocks in Sicily nor in Italy till 

 I approached the foot of the Alps ; and in Sweden I found them in- 

 creasing in number and size as I advanced northwards, where I saw 

 some between thirty and forty feet in diameter. The erratics, there- 

 fore, as far as my experience extends, are a northern phaenomenon ; 

 and M. Charpentier states, on the authority of Humboldt, th&t 

 there are no such fragments at the eastern foot of the equatorial 

 Andes, where, notwithstanding the altitude of the mountains, there 

 are no glaciers. 



But assuming that ice could have transported into their present 

 position those myriads of angular blocks which cover the low coun- 

 tries bordering the Baltic, in what manner and by what force could 

 these masses have been detached from the mountains of which they 

 once formed a part ? Now the granitic rocks in Sweden sometimes 

 consist of large tabular masses, traversed by numerous horizontal 

 and vertical joints ; and entire hills may be said to be broken up, in, 



* Sur les Blocs errat. de la Suisse, Ann. des Sci,, torn. viii. p. 219. Mr. 

 Bakewell has also in some one of his works alluded to the carrying of Alpine 

 blocks by ice. 



