98 ^ NEW YORK STATE MUSEUM 



into the Genesee river, and then from a point near Leroy, Allen's 

 creek, flowing east into the Genesee, while north of this, Black 

 creek drains part of the Oak Orchard swamp and flows into the 

 Genesee river; flowing west from Oakfield, the Oak Orchard creek, 

 which breaks through the Niagara escarpment at Medina, while 

 west of this, the Tonawanda creek completes the line across the 

 State and takes the drainage of this part of the State to the 

 Niagara river. 



An examination of the topographic atlas sheets of this part of 

 the State shows that there are many elevations within the Salina 

 depression fully as high as the Niagara escarpment. The fact, 

 however, that the drainage of the country overlying the Salina 

 deposits extends in an east and west direction, and that the 

 tributaries of the main streams flow south from the Niagara ridge 

 and north from the Helderberg and higher deposits, gives unmis- 

 takable proof that there is here a valley about 180 miles long 

 extending from the vicinity of Utica to the Niagara river. In 

 some parts, the valley is double; this is to be seen west of the 

 Genesee river, where we have Allen's creek and Black creek about 

 10 miles apart. In the Finger Lake region, it is also double, as 

 is seen north of Seneca and Cayuga lakes, where the Seneca river 

 and the Clyde river flow parallel to each other. In speaking of 

 this region of the State as a depression, it is not the aim of the 

 author to give the impression that it is a broad valley bounded 

 by two ridges. It is rather a rolling plain with many small hills, 

 few of them exceeding 100 feet in hight above the level of the 

 valley. 



Formation. Though there is now a marked depression, in 

 former times the depth of the valley was much greater than at 

 present, andj in order to determine the time and manner of its 

 formation, it becomes necessary to consider the agencies that 

 were active in cutting the valley and filling it again. 



The continental ice sheet has been considered the most active 

 agent in determining all slight irregularities in surface con- 

 figurg^^ion; but, for reasons that will be set forth in another 



