206 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



by the direction of the furrows : in New England from N.N.W. to 

 S.S.E. ; in the valley of the St. Lawrence from north-east to south- 

 west. 



With regard to evidence of the age of the boulder formation of 

 North America, I am not aware of any having been met with that 

 connects it with a period so early as in Denmark ; it contains in 

 many places shells identical in species with those now living in the 

 adjoining seas. The detritus in which the bones of Mastodon are 

 buried at Big-Bone-Lick, in Kentucky, Mr. Lyell is inclined to be- 

 lieve to be more modern than the northern drift. 



In the last number of the ' Edinburgh Philosophical Journal' are 

 two valuable papers relating to erratic blocks, grooved surfaces, and 

 the action of glaciers ; the one by Mr. Maclaren, to which I have 

 already referred, the other by Professor James D. Forbes. The 

 paper of Mr. Maclaren describes grooves and striae which he ob- 

 served last summer on the rocks on each side of the Gare Loch, in 

 Dumbartonshire, and these, together with blocks and an accumulation 

 of loose materials resembling a terminal moraine, appear to indicate 

 very clearly the former existence of a glacier in the space inclosed 

 between the hills that bound the loch. He also observed numerous 

 rounded blocks in the same locality, which could not have been pro- 

 duced by the same glacier, for they consist of granite, some of great 

 size, as much as five feet in diameter, at various heights on the hills — 

 one on the top of a hillock, 320 feet above the loch ; and no granite, 

 no parent-rock to which they can be traced is nearer than forty 

 miles to the north. But between the localities where they now exist 

 and that parent-rock there are ridges, over which they must have 

 travelled, that are 1500 feet above the present sea-level. This then 

 is a case analogous to that of the Valdai Hills in Russia, on the 

 southern flanks of which blocks of Scandinavian granite are scat- 

 tered, indicating that these hills, and in like manner the summits of 

 the barrier north of Gare Loch, were a sea-bottom, upon which the 

 blocks were dropped from floating icebergs; that sea-bottom being 

 subsequently raised, to form the existing land. 



The principal object of Professor Forbes's paper is to describe 

 the topography and geological structure of the Cuchullin Hills in 

 Skye. He gives us much new and interesting information respecting 

 the igneous rocks, of which they are composed, particularly that 

 comparatively rare variety, hypersthene rock : but he also describes 

 these same rocks as being furrowed and polished in several of the 

 valleys, but especially in the valley of Coruisk, the furrows there 

 radiating from a centre to the sea-shore, and, in his opinion, they 

 demonstrate in as clear a manner as the subject admits of, the for- 

 mer existence of a glacier in that locality. AH will admit that the 

 opinion of Professor Forbes on this subject is one in which we may 

 place entire confidence. The hypersthene rocks "are smoothed and 

 shaven in a direction parallel to the length of the valley wherever 

 their prominent parts are presented towards the head of the valley ; 

 but towards the sea, they are often abruptly terminated by craggy 

 surfaces, showing the usual ruggedness of the natural fracture of 



