INTRODUCTION. 425 



The phenomena are complex and singularly interesting, and the de- 

 termination of the several water-levels, involving the facts concerning 

 the nature and sequence of the geologic events, reveal a fine problem in 

 glacial geolog}^ which is thought to have been solved in its general 

 features. A vast body of interesting details remains unstudied. 



The work upon the region was done in the late autumn of 1894 and 

 the summer of 1895. The data relating to the water-planes were col- 

 lected without reference to their bearing, and with only indefinite idea 

 or theory as to the corresponding outlets. The latter, indeed, were not 

 wholly known and the correlation of the planes of the static waters with 

 the several outlets has been completed since leaving the field. 



The largest part of the work has been the determination of altitudes.* 

 With no topographic map of the region, the railroad " levels " have been 

 the only data available. While these may, in some cases, have an error 

 of perhaps a few feet, it can never be sufiicient to compromise the con- 

 clusions of the paper. 



The present Genesee Valley. 

 hydrography and topography. 



The general hydrographic features of the area are so w^ell shown by 

 the accompanying map f (plate 19) that much verbal description can be 

 omitted. * 



Among the rivers of New York the Genesee is remarkable for its length, 

 direction of flow" and amount of fall. From its sources in Potter county, 

 Pennsylvania, to its mouth at lake Ontario, the distance in a right line 

 on the map is 100 miles. The total length of the river in all its windings 

 is at least one-half more. 



The altitude of the cols in which the east and middle branches of the 

 river head is over 2,200 feet above tide, while the enclosing tableland is 

 one or two hundred feet higher; so the fall in the stream from its origin 

 to lake Ontario (247 feet above tide) is about 2,000 feet. The inclination 

 of the basin at the time of the ice-retreat was probably a few hundred 



* The writer would here express his gratitude to the many persons who by personal assistance 

 and various courtesies have aided in the w^oik. Especial thanks are due to the following gentle- 

 men : Professor J. P. Slocum, Angelica; Professor A. J. Glennie, Bolivar; Mr George W. Pierce, 

 Canisteo, engineer N. Y. and P. railroad; Mr M. S. Blair, Hornellsville, superintendent C. N. Y. 

 and W. railroad Mr C. R. Neher, Rochester, division engineer W. N. Y. and P. railroad; Mr 

 Geoi'ge A. Thompson, Rochester, and Mr H. E. Gilpin, Hornellsville, division superintendents of 

 the Erie railroad. 



f The basis of this map is the map accompanying the report of Mr John Bogart, state engineer 

 and surveyor, on the Supply of Water from the Genesee River to the Erie Canal, 1890, 



