On the former Changes of the Alps. 35 



had been forced under the edges of the very rocks out of 

 whose detritus they had been formed. 



Before this great revolution had tajien place no large 

 erratic blocks were known, but after it they became common, 

 and were the necessary production of that intensely cold 

 climate to which the Alps were then subjected ; a change of 

 which their surface bears distinct evidence. 



During the same period the low countries of northern 

 Europe were covered by an Arctic sea. If such waters then 

 extended to the Jura and the Alps, icebergs and rafts must 

 have been detached from the latter, carrying away blocks of 

 stone northwards, to be dropped at intervals, just as it has 

 been demonstrated that the Scandinavian blocks were dropped 

 in Prussia, Poland, and the low lands of Russia, when all 

 those regions were under the influence of an Arctic sea. 

 Bavaria, and the lower parts of the Cantons Vaud, Neuf- 

 chatel, and Berne, were, it is supposed, then covered by 

 waters which bathed the foot of the Alps. 



That the change from a former genial climate to the first 

 great period of cold was a sudden one is further sustained 

 by the fact, that the inclined strata in which the Mediterra- 

 nean animals are buried, are at once covered transgressively 

 and unconformable by other beds of gravel, shingle, and mud, 

 in which the remains of plants and animals are those of a 

 cold climate. 



The third scene, therefore, exhibited the sands and pebbles 

 of the genial period thrown up into mountains on the flanks 

 of the chain, the peaks of which were probably covered for 

 the first time with snow, and from the openings of which, 

 whether protruding to the sea-shore or into deep fiords or 

 bays, glaciers and their moraines advanced, from which ice- 

 bergs or rafts were floated away as suggested. 



In concluding. Sir Roderick thus expressed himself: — 

 " Having thus now conducted you rapidly through the most 

 prominent changes which the Alps have undergone, from 

 the first period when they had emerged, probably as an 

 archipelago of low islands in a tropical climate, to that 

 epoch when the animals and plants living upon them indi- 

 cated a Mediterranean temperature, and then to that Arctic 



c2 



