526 On the Distribution of the Superficial Detritus of the Alps. 



In considering the distribution of the erratic detritus of the Rhone, 

 Sir Roderick having denied that it can ever have been carried down 

 the chief valley to the Lake of Geneva in a solid glacier, still more 

 insists on the incredibility of such a vast body of ice having issued 

 from that valley, as to have occupied all the low country of the can- 

 tons Vaud, Friburg, Berne and Soleure, and to have extended its 

 erratics to the slopes of the Jura, over a region 100 miles in breadth 

 from north-east to south-west as laid down in the map of Charpen- 

 tier. He maintains that in the low and undulating region between 

 the Alps and the Jura, the small debris derived from the former has 

 everywhere been water- worn, and that there is in no place anything 

 resembling a true moraine ; and he therefore believes, that the great 

 granitic blocks of Mont Blanc were translated to the Jura by ice- 

 floats, when the intermediate country was under water. He further 

 appeals to the water- worn condition of all the detritus of the high 

 plateaux around Munich, 1600 and 1700 feet above the sea, to show 

 that a subaqueous condition of things must be assumed when the 

 great erratic blocks were carried to their present positions. 



Prof. Guyot of Neufchatel has endeavoured to show, that the de- 

 tritus of the rocks of the right and left sides of the upper valley of 

 the Rhone have also maintained their original relative positions in 

 the great extra Alpine depression, and that these relations are proofs, 

 that nothing but a solid glacier could have arranged the blocks in 

 such linear directions. But the author meets this objection by 

 suggesting that there are notable examples to the contrary. He also 

 refers to the great trainees of similar blocks which preserve linear 

 directions in Sweden and the low countries south of the Baltic, to 

 show that as this phaenomenon was certainly there produced by power- 

 ful streams of water, so may the Alpine detritus have been arranged 

 by similar agency. In alluding to the drainage of the Isere he further 

 points to the admission of Prof. Guyot, that nearly all its erratic de- 

 tritus, both large and small, is rounded and has undergone great at- 

 trition ; and he quotes a number of cases in which such boulders and 

 gravel, derived from the central ridges of Mont Blanc, have been 

 transported across tracts now consisting of lofty ridges of limestone 

 with very deep intervening valleys ; and therefore he infers that the 

 whole configuration of these lands has been since much changed, in- 

 cluding the final excavations of the valleys and the translation of 

 enormous masses of broken materials into the low countries of 

 France. 



In conclusion it is suggested, that the dispersion of the far-travelled 

 Alpine blocks is a very ancient phsenomenon in reference to the 

 historic sera, and must have been coeval with the spread of the 

 northern or Scandinuvian erratics, which it has been demonstrated 

 was accomplished chiefly by floating ice, at a time when large 

 portions of the Continent and of the British Isles were under the 

 sea. Viewing it therefore as a subaqueous phsenomenon. Sir 

 Roderick is of opinion that the transport of the Alpine blocks to 

 the Jura falls strictly within the dominion of the geologist, who 

 treats of bygone events, and cannot be exclusively reasoned upon by 

 the meteorologist, who invokes a long series of years of sunless and 



