'S94-] 36.S [Grabau. 
center of this valley. At Le Roy and beyond, the outHne of the 
valley becomes less distinct, owing to the softer charactei- of the 
rock forming its sides, and to the more extensive depositpf drift 
material. Its continuation is presumably indicated by the Oatka, 
though this cannot be said with certainty. 
The valley east of the Genesee extends from Dansville to Mt. 
Morris, where it joins the valley now occupied by the Genesee 
between Mt. Morris and Rochester, above described as the third 
portion of the modern channel. It is, in fact, a southward con- 
tinuation of the latter ; and, except that its sides are better 
defined, it has the same character, maintaining an almost i;niform 
elevation of about 600 feet above sea level. It is to-day occupied 
by the Caneseraga, a small stream emptying into the Genesee at 
Mt. Morris. 
For the sake of clearness in description it will be best to give 
each of these valleys a separate name. First, I shall apply the 
name Genesee Valley exclusively to the valley south of Portage- 
ville, in which the river flows to-day from its source to that village. 
Secondly, the valley from Dansville to Mt. Morris, and thence to 
Rochester, which, as a whole, is commonly called the "Genesee 
Valley", though only the northern half is occupied by the modern 
Genesee, I will call the Dansville-Rochester Valley. Finally, 
the valley in which Warsaw is situated I will call the Wyoming 
Valley, the name commonly applied to it, its major portion being 
in Wyoming County. The modern Genesee, then, has its first 
portion in the Genesee Valley, and its third portion in the Dans- 
ville-Rochester Valley, the other portions being in postglacial 
gorfjes. 
Relations and DEVELOrMENX of the Valleys. 
Genesee and Wyoming Valleys. — In order to trace out the 
relations between these valleys it becomes necessary to look for 
the continuation of the Genesee Valley from Portageville north- 
ward. Standing at the head of the gorge opposite Portageville 
and facing in the direction of the river, we find on the right an 
immense deposit of drift material rising three hundred feet or 
more above the river bed. This deposit, which is in the form of 
a narroAV, level-topped ridge, I will call the Portage Ridge. 
(See fig. 2.) Borings have proved the absence of rock to such 
a depth that, even without further proof, we should be warranted 
