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others, oS the former presence of inland lakes in North America 

 larger than those which no\v prevail, has recently been sustained 

 by the Rev. Mr. Schoolcraft, an American geographer, in a memoir 

 which he read before the Geological Section of the British As- 

 sociation at Manchester. This author, who has passed nearly 

 twenty years of his life in their vicinity, believes that the former 

 great lakes have been lowered by ancient dislocations. As examples 

 of the bottoms and edges of these former sheets of water, he adduces 

 large belts and tracts of sandy plains, which, from their scanty vege- 

 tation and undulated surfaces, have all the appearance of recent desic- 

 cation; and as proofs of the water having stood at various levels, he 

 states, that it has left marks of erosion on the mural faces of the 

 harder rocks. But the most original part of this communication, and 

 which may indeed serve to explain the origin of some of the ridges 

 respecting v.'hose origin Mr, Lyell differs from the writers before 

 alluded to, is the actual production of sand-storms by causes associ- 

 ated with these lakes. Indicating some of the most extensive enei'gies 

 of this nature proceeding from Lake Superior, and the powerful 

 action of storms upon sandstone and grauwacke rocks, Mr. School- 

 craft is of opinion, that by a union of powerful currents and furi- 

 ous gales, dunes have been formed which rise to 300 feet above 

 the water. The sand, being first worked up in great bars, has since 

 been transported by the wind over wide tracts, which are thus ren- 

 dered sterile; stagnant pools are formed in adjacent depressions, 

 once highly productive, and prostrated and buried trees are there 

 associated with freshwater shells ; and thus by actual causes, forma- 

 tions of considerable thickness are accumulated. Geologists have 

 long been aware, that wind has been an agent in heaping up some 

 of the deposits whose origin they endeavour to explain, antl very 

 striking examples of this operation were adduced by Lieut, (now 

 Capt.) Nelson, R,E., in his account of the modern shelly and sandy 

 limestone of the Bermudas. As no one, indeed, has a better acquaint- 

 ance with this class of phsenomena than Mr. Lyell, it is enough for me 

 to have attracted his notice to the vivid descriptions of Mr. School- 

 craft, which may, I think, aid in explaining some of the superficial 

 appearances in the lake country of North America. 



Let us return, however, to the memoirs of Mr. Lyell. Reviewing 

 the series of changes which have taken place in the Canadian and 

 Lake region, Mr. Lyell conceives, that after an early period of emer- 

 gence, during which lines of escarpment and valleys of denudation 

 were excavated in solid rocks, the surface of the country was 

 submerged, and the cavities filled with the marine boulder forma- 

 tion ; and that during the last elevation of the land, the parallel sand 

 ridges were produced, the boulder formation partially denuded, and 

 the different lakes' probably formed in succession, leaving a partial 

 sea channel, which, contracting first into an estuary, was eventually 

 converted into the river Niagara. Reaching this point in his order of 

 events, our author succeeds most happily in developing his views 

 concerning the retrocession of the falls of this river ; bringing for- 

 ward arguments to show that during the re-emergence of the land 



