32 REPOET OF THE SECEETAEY. 



diffusing information derived from the experience of the Smithsonian 

 Institution, especially wanted at this time, when so many new institu- 

 tions are about to be organized ; but they would be out of place in 

 this report, though they may be given in the appendix or elsewhere. 



Whittlesey on the Drift. — The following is an account of the paper 

 on the drift before mentioned which has not yet been described. 



The term drift, as employed in geology, includes the collection of 

 gravel, sand, clay, and stones occurring over portions of the conti- 

 nent without stratification or order of arrangement, and which have 

 evidently been transported and distributed without the agency of 

 rivers. For the study of this formation in the territory north of the 

 Ohio river and east of the Mississippi to the national boundary, Mr. 

 Whittlesey claims to have had special opportunities during the past 

 twenty -five years. The length north and south of this area is about 

 eleven degrees of latitude, from the 38° to the 49°, its breadth being 

 quite irregular. Its eastern boundary is a line passing through the mid- 

 dle of the system of North American lakes, and to the west it extends at 

 least to the Lake of the Woods. Over this space he has found what he 

 considers but one formation, belonging to the post-tertiary, wholly of 

 fresh-water origin, no remains as yet having been foundx>f a salt water 

 character, while to the eastward of Lake Brie, in the valleys of Lakes 

 Ontario and Champlain, and the River St. Lawrence, the shells which oc- 

 cur are wholly marine. Further examination he supposes will show that 

 the fresh- water formation overlaps the marine, and is consequently more 

 recent. The thickness of the fresh-water drift is variable, in some 

 places from 600 to 1,000 feet, though it seldom exceeds 200 or 300 

 feet. The author uses the term glacial drift to describe this forma- 

 tion as expressing what he conceives to be its origin in accordance 

 with the theory originally proposed by Professor Agassiz, viz., an im- 

 mense sheet of ice, at first principally confined to the pole of 

 greatest cold, but gradually increasing its area by accumulations of 

 snow in winter on its central part, and by the thawing in summer of 

 the surface, the subsequent freezing "and expansion of the infiltered 

 water producing a slow but almost resistless motion outward in 

 every direction from the centre. This sheet of ice, like the modern 

 glacier, having fragments of hard stone imbedded in its lower sur- 

 face, would furrow and grind the rocks underneath — would bear on 

 its upper surface, and within its interior, boulders and fragments of 

 rocks which fell on it in its passage through mountain gorges, or 

 which it tore from their sides, and, in addition to these, would carry 

 with it the materials eroded in its passage; and finally, on melting, 



