582 Geological Society : Annivei'sary Address, 184-2. 



have obstructed the road-ways or passes of our ancestors. Thus is 

 the supposed anomaly explained without recurring to any change 

 of climate*. 



In that part of our own country to which the glacial theory has 

 been applied, Mr. Charles Maclaren, already known to you by ex- 

 cellent geological treatises, has recently published a well-condensed, 

 small work explaining the views of Agassiz. The pha^nonlena of 

 glaciers and the general doctrines derived from their study being 

 explained, JNIr. Maclaren proceeds to analyze those cases of trans- 

 ported detritus in the neighbourhood of Edinburgh to which the 

 theory had been supposed to apply. 



A year and a half only has elapsed since Professor Agassiz and 

 Dr. Buckland seemed to think, that this district was as rich in 

 proofs of the action of glaciers as many other parts of Scotland 

 which they visited, and as I happened to witness the efforts of my 

 predecessor in this Chair to attach Mr. Maclaren to his views, I 

 must be permitted to direct your attention to the practical results 

 at which this gentleman has arrived, iu some prominent cases. 



Observing blocks of greenstone on Arthurs Seat, which, from 

 their peculiar structure, must have been transported from Salisbury 

 Craigs, a lower hill, and separated from the former by an abrupt val- 

 ley, Mr. Maclaren infers, that if the present surface of the land be 

 argued upon (and in all questions of glaciers this is a postulate), nei- 

 ther glacier, nor icebei'g, nor current will explain the fact. It is un- 

 necessary that I should here examine this author's hypothesis, by 

 which in order to solve the local problem, he restores the inclined 

 stratified masses of Salisbury Craigs to such an extent as to give 

 them an altitude in ancient times superior to that of Arthur's Seat ; 

 for whether we adopt his ingenious view, involving a mighty sub- 

 sequent denudation, or suppose that in the oscillations of this plu- 

 tonic tract the former low and higli points of land have been re- 

 latively depressed and elevated, it is obvious, from the very struc- 

 ture of the rocks, that in both cases a subaqueous, and not a sub- 

 aerial condition is called for to explain the appearances, and this 

 too, be it recollected, on the summits of the highest hills in tiie im- 

 mediate vicinity of the Scottish metropolis, in and around which 

 the action of glaciers has been supposed to be visible at much lower 

 levels ! 



Among the examples of the scratched and polished surfaces of 

 rocks near Edinburgh, I do not perceive that the glacialists have 

 grappled with certain appearances on which Dr. Buckland for- 

 merly dwelt with so much pleasure, viz. the grooved or channeled 



* I hoped to have been able to quote the opinions of Professor J, 

 Forbes on this vexata cjucesHo, because it is well known that he was a 

 companion of Professor Agassiz in the Alps during the last summer, but 

 this distinguished cultivator of physical science has not yet published his 

 views on the action of glaciers as affecting the surface of the earth, though 

 he has given to the public a very ingenious sketch, descriptive of a peculiar 

 pamllel striation in the solid ice of glaciers. — Edinburgh New Philoso- 

 phTcal Journal, January, 1842. 



