ANNIVERSARY ADDRESS OF THE PRESIDENT. 201 



land were deposited upon a sea-bottom which has been since upraised. 

 Where the smaller detritus and rounded boulders came from, and 

 how they were drifted into their present situations, are branches of 

 the subject involved in great obscurity. That fragments of hard 

 rocli were the tools which graved the furrows and striae, and polished 

 the surfaces of hard rocks they passed over, is pretty evident ; but 

 what held and guided the tool, what force applied it, to what extent 

 ice, and to what extent water was the agent, is not so clear ; that 

 both have acted there can be no doubt. It is, I think, very satis- 

 factorily shown, that the erratic blocks must have been brought down 

 from lofty mountains, to the open sea that washed their bases, by 

 glaciers ; that they were floated to great distances by masses of ice 

 breaking off from these glaciers, to form icebergs, in different direc- 

 tions from central points, and stranded on elevated parts of the sea- 

 bottom, without having been subject to much attrition ; and, more- 

 over, that these erratic blocks can, in a great number of instances, 

 be traced to their parent rock, though now separated some hundred 

 miles. Some of the evidence in support of these positions, supplied 

 during the last year, I will now bring forward. I regret that my 

 limits will not allow me to do greater justice to the authors to whom 

 we are indebted for it, either as regards their facts, or their deduc- 

 tions from these facts. 



The boulder formation and erratic blocks cover an enormous 

 area, from the Arctic Sea over a great part of Northern Europe ; 

 not continuously, but often uninterruptedly over vast regions. The 

 masses of clay, sand and gravel are sometimes of so great thickness 

 that it is impossible to detect a trace of the subjacent solid rock, 

 over very wide tracts, even in the beds of the Volga and the deepest 

 cutting rivers. M. Durocher, in his first memoir*, did not trace the 

 erratic blocks farther east than the forty-second degree of longitude, 

 nor farther south than the fifty-fifth degree of north latitude; but 

 the authors of the 'Geology of Russia' have described them as ex- 

 tending 500 miles farther east, and above 200 miles farther south. 

 As the parent rocks of most of these huge fragments are in Scan- 

 dinavia and Finland, they have been in some instances transported 

 to a distance of 800 miles in a direct linef^ It is possible that the 

 boulder formation may extend somewhat farther, but probably not 

 much ; for there is reason to believe that land on the east and south 

 was above the level of the sea, as has been already stated, at the 

 time the country to the west and north was submerged, which would 

 stop the advance of the boulder formation and erratic blocks, but in 

 an irregular line. No erratic blocks of northern origin have been 

 seen for a considerable distance westward of the Ural Mountains. 



There is a feature in the character of this superficial covering of 

 detritus which is very important to attend to in tracing its history, 

 viz. that the materials are not always the same ; that the principal 

 mass in each district is of local origin, and very clearly besj)eaks its 

 derivation to be in the subjacent rocks ; and that the great northern 



* Comptcs Rendus, Janvier 1842. f Map accompanying ' Geology of Russia.' 



