iS94-]- 359 [Gnibau. 
THE PREGLACIAL CHANNEL OF THE GENESEE 
RIVER. 
BY AMADEUS W. GKAliAU. 
Physical Features of the Region. 
The Genesee River takes its rise in the liighlands of northern 
Pennsylvania, and, entering the state of New York in Allegany 
County, continues to flow in a northwesterly direction for about 
thirty miles. Near the village of Caneadea it alters its course to 
east of north, which general direction it maintains until it enters 
Lake Ontario, nine miles north of Rochester. The river thus 
traverses the entire state from south to north, dividing it into 
two unequal portions. It also forms a natural boundary-line 
between the "Finger Lake" region in central New York and the 
almost lakeless western district. 
Analysis of the modern channel. — The present channel of the 
Genesee admits of a division into four portions. Beginnino" at 
the south, we find a well-defined, broad, and usually flat-bottomed 
valley, with sloping sides which are drift covered, and, as a rule, 
heavily wooded. This is, in fact, a mature, preglacial river 
valley, cut out of the Chemung and Portage shales and sand- 
stones which are only exposed in the lateral ravines, or cuttings. 
Through this valley the river pursues a meandering course, with 
banks composed of sand and clay, over which it annually rises, 
flooding the adjacent "flats." The depth at which rock would 
be found has not been ascertained ; but, as will appear later, the 
valley seems to have been filled up to a considerable extent. The 
bottom of the valley at Portageville has an elevation of 1,050 
feet A. T., and is composed mainly of alluvial material. While, 
however, the general nature of the valley bottom is flat, we find 
occasionally kame-like hills of sand and gravel, of the sugar-loaf 
type common in that region, and an occasional accumulation of 
till. 
Opposite the village of Portageville, the valley appears to come 
to an end, the river entering upon the second portion of its 
channel, a rocky gorge over twenty-five miles in length, extend- 
ing from Portageville to Mt. Morris. This gorge varies in width 
