Boulder Formations and Erratic Blocks. 323 



northern origin. An instance of this last occurs at Brooklyn, 

 near New York. 



In the United States, Canada, and Nova Scotia, where the 

 gravel or drift has been removed, the rock immediately subja- 

 cent is very frequently furrowed and striated, and here and 

 there flattened domes of smoothed rock {roches moutonnees) are 

 met with. The furrows have been found in the New England 

 hills at all heights, even to as much as 2000 feet. In one place, 

 on the summit of a high hill of sandstone, Mr Lyell saw an 

 erratic block of greenstone 100 feet in circumference. The 

 erratic blocks and boulder formation have been transported 

 southwards along the same lines as are marked out by the di- 

 rection of the furrows : in New England, from NNW. to 

 SSE. ; 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 believe to be more modern than the 

 northern drift. 



In a late number of Jameson's Edinburgh New Philosophical 

 Journal are two valuable papers relating to erratic blocks, groov- 

 ed 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 observed 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 produced 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 



