Boulder Formations and Erratic Blocks. 315 



so, before a sufficient mass of observations can be collected 

 on which a satisfactory solution of it can be founded. Al- 

 though, as regards Europe, many important local facts, ex- 

 hibited in limited districts, have been well described by seve- 

 ral geologists, both of this country and of the continent, we 

 are indebted, for the most extended observations and the 

 most comprehensive views of the subject, to the labours of 

 Keilhau, Sefstriim, Durocher, Murchison, De Verneuil, and 

 Forchhammer. The geologists of the United States, and 

 Lyell, have brought together a great body of evidence re- 

 specting the same phenomena in North America. There is 

 reason to infer, from the limited observations that have been 

 made along the shores of Siberia, that the boulder formation 

 extends also over Northern Asia. 



Many new observations have been made known to us dur- 

 ing the last year, by the authors of the " Geology of Russia," 

 by Mr Lyell, in his " Travels in the United States, Canada, 

 and Nova Scotia," and by M. Durocher, in an additional me- 

 moir which he read last December before the Geological So- 

 ciety of France, describing observations made by him in Nor- 

 way during the preceding summer. 



You are aware that Agassiz and Charpentier have at- 

 tempted to explain the phenomena, by supposing that, at a 

 very recent geological period, since the time when the land 

 had assumed its present form, Northern Europe was covered 

 with a vast mantle of ice ; and that the detritus and erratic 

 blocks have been formed and transported by the agency of 

 sub-aerial glaciers, in the same manner as moraines have 

 been accumulated, blocks transported, and rocks furrowed, 

 striated, rounded, and polished, by the glaciers descending 

 from the Alps. Abundant evidence has been brought for- 

 ward to demonstrate, that by no such action can the pheno- 

 mena be explained ; and all the geologists mentioned above, 

 who have carefully investigated them, reject the theory as 

 inapplicable to Northern Europe and America, except in a 

 very limited sense. 



The Boulder Formation, or Northern Drift, and The 

 Erratic Blocks, are shewn, by the authors of the " Geology 

 pf Russia," to be two distinct classes of phenomena ; the lat- 



