Professor Agassiz on (he Glacial Theory. 219 



demy, not a scientific society, in which the erratic phenomenon 

 has not been discussed and sui)ported by new facts ; and such 

 has been the activity displayed by the savans of every coun- 

 try, that the most succinct abstract of the works and memoirs 

 on the subject which have appeared within the last two years, 

 would greatly exceed the limits of an article like the present. 

 M. de Charpentier, in his Essai sur les Glaciers et le Terrain 

 Erratique, has described in detail the traces of ancient glaciers 

 in the great valley of the Rhone and its lateral valleys, and 

 also at a multitude of other points in Switzerland ; M. Studer 

 has observed them on the southern side of the Alps ; and Mr 

 Martins in the Grisons. The French geologists assembled at 

 Grenoble in 1840 studied them in the Alps of Dauphiny, and 

 made them the subject of their discussions at the meeting held 

 at Lyons in 1841. The polished rocks, in particular, seem t^- 

 be very distinct on Mount Cenis, where they have been de- 

 tected by Mr Trevelyan and by Captain Le Blanc. MM. Re- 

 noir, Hogard, and Le Blanc have continued to observe the 

 erratic phenomenon in the Vosges ; MM. Max Braun and Du 

 Rocher have noticed it in the Pyrenees; and I myself have done 

 so in the Black Forest. The Swiss and French Jura has in this 

 respectbeenmade the object of continued study by MM. Gressly, 

 Guyot, and Desor, who have proved that the erratic blocks of 

 the Alps extend far beyond the limits assigned them by MM. 

 de Buch and Charpentier ; and, lastly, I have discovered er- 

 ratic blocks, accompanied by polished and scratched surfaces, 

 in a host of localities in the Alps, where they had not pre- 

 viously been known to exist. 



The great phenomena of the north, although attributed to 

 other causes, do not the less belong to the same subject ; and, 

 since the investigations of MM. Alexander Brongniart and Sef- 

 strtim, they have been made the object of continued researches 

 by MM. Bothlingk, Nordenskiold, Eichwald, Durocher, Robert, 

 Martins, Murchison, De Verneuil, and Kaiserling. Finally, the 

 American geologists, also, have very recently noticed a vast 

 net-work of polished rocks and erratic blocks in the United 

 States. 



But it is more particularly in Great Britain that the most 

 unexpected discoveries have been made. Who could have sup- 



