Address before the Association of American Geologists. 253 



cerning which so little of geological importance has been known. 

 Henceforth, however, glacial action must form an important 

 chapter in geology. While reading this work and the abstracts 

 of some papers by Agassiz, Buckland and Lyell, on the evidence 

 of ancient glaciers in Scotland and England, I seemed to be n.c- 

 quiring a iiev) geological sense ; and I look upon our smoothed 

 and striated rocks, our accumulations of gravel, and the tout en- 

 semble of diluvial phenomena, with new eyes.* The fact is, 

 that the history of glaciers is the history of diluvial agency in 

 miniature. The object of Agassiz is, first to describe the minia- 

 ture, and then to enlarge the picture till it reaches around the 

 globe. 



The glaciers are vast masses of ice, often leagues in extent, 

 formed of melting and freezing snow, which are sent out from the 

 summits of the Alps by the force of expansion into the valleys 

 below, often to the distance of twelve or fifteen miles. Those 

 elevated and wide plateaux, called in Switzerland Mers de Glace, 

 exhibiting only one thick sheet of ice, through which the crests 

 and summits of the mountains sometimes rise like volcanoes, are 

 the grand source or birthplace, of the glaciers. In their descent 

 they plough their way through the soil, pile up pebbles and sand 

 along their sides and at their extremities, and even upon their 

 backs ; which, upon the retreat, or melting of the glacier, consti- 

 tute moraines, and correspond exactly in composition and shape 

 to those accumulations of gravel and bowlders that have been as- 

 cribed to diluvial action. The stones and sand frozen into their 

 lower surface, also, like so many fixed diamonds, smooth and fur- 

 row the surface of the rocks in precisely the same manner as they 



* I trust that the members of the Association will pardon me for having made 

 some alterations in the form, though not in the leading thoughts, of this part of 

 my Address, since it was delivered. They will recollect, that while I expressed a 

 very favorable opinion of the Glacial Theory, so far as I understood it, I staled that 

 I had not seen the work of Agassiz named in the text. Through the kindness of 

 Prof. Silliman, I have since been favored with the perusal of the copy of this 

 work which, with its splendid alpine illustrations, he received from the author. I 

 am indebted, also, to Dr. J. Pye Smith, of London, for an abstract of the papers of 

 Agassiz, Buckland and Lyell, read before the London Geological Society last au- 

 tumn, on the ancient glaciers of Scotland and England. A flood of light having 

 thus been unexpectedly thrown in upon my mind, I am free to acknowledge that 

 many of my difficulties in respect to this theory have been removed, and that the 

 great mass of evidence in its favor, thus brought before me, has led me to express 

 a warmer admiration of its leading features and a greater readiness to adopt its lead- 

 ing principles, although satisfied that it will need important modifications. 



