ANNIVERSARY ADDRESS OF THE PRESIDENT. 207 



the rock, and exhibiting the phsenomenon of Stoss Seite and Lee 

 Seite, so often described in the Scandinavian rocks." 



" When the same rock is traversed by claystone veins, or by veins 

 of crystallized hypersthene and magnetic iron, these various parts of 

 such different hardness are all uniformly shaven over, in conformity 

 with the general form of the mass to which they belong. This 

 presents a striking analogy to the phsenomena of polished rocks in 

 the Alps, where the quartz veins are cut off parallel to the surface 



of the bounding felspar The furrows are not confined to the 



entrance of the valley, but extend to the upper part of it, and to a 

 great height above its level, particularly on the west side, where the 

 faces of these almost vertical cliffs of adamantine hardness are scored 

 horizontally, as potter's clay might be by the pressure of the fingers, 

 or like the moulding of a cornice by the plasterer's tool." 



The question naturally arises, at what period were these valleys 

 in Dumbartonshire and in Skye occupied by glaciers ? That they 

 were so after the land had been formed into the present mountains 

 and valleys is obvious ; but that defines no particular period. We 

 have in the Gare Loch two distinct classes of phsenomena, which 

 could not have been produced either by the same agents or at the 

 same time. We have proof of the action of sub-aerial glaciers ; we 

 have also proof that there are erratic blocks that could not have 

 been brought into their present position unless the ground on which 

 they rest had been submerged : they were dropped, it is most rea- 

 sonable to suppose, from icebergs floating in a sea, and arrested by 

 elevations in the sea-bottom. During such submergence there 

 could be no glaciers in the valleys of Gare Loch or Coruisk. Are 

 we to suppose that after these valleys had been occupied by a gla- 

 cier, and the erosions had been made, the land sank down, conti- 

 nued for a long interval as a sea-bottom, during which time the 

 glaciers melted away, and that the land again emerged, bearing the 

 erratic blocks upon it ? The subject is one of vast difficulty ; but 

 the phaanomena evidently involve great changes in the condition of 

 the land, and consequently, perhaps, in the climate of that region. 



It is an important feature in the history of the boulder formation, 

 that the mode of its accumulation, and the direction of the channels, 

 furrows and striae worn in the rocks, indicate a force coming from 

 the north between N.W. and N.E. The worn and polished surfaces 

 of BO many rocks facing the north, while their rugged unworn sur- 

 faces point to the opposite direction, are farther proofs of the same 

 movement. The travelled rounded boulders and detritus from the 

 middle of Sweden and Norway southward must therefore have been 

 derived from land existing north of that latitude. 



Submarine currents arc by many geologists supposed to have 

 been the moving power ; and it is also said, that the detrital matter 

 they hurried along smoothed and polished the rocks they met with 

 in their progress, and graved the furrows and strioe. \Ve ns yet 

 know little of the existence, at great depths, of submarine currents?, 

 or of their power of transporting heavy materials. Sir II. Murchi- 

 son, referring to the generation and power of what Mr. Scott llus- 



