72 



AX AMERICAN GEOLOGICAL RAILWAY GUIDE. (N.Y.) 



35. Irondequoit. A few miles east of the mouth of the Genesee River, the Irondequoit Creek 

 empties into the lake, flowing in a deeper channel than the Genesee, hut through deposits of sand 

 and gravel. Professor Hall suggests with much probability, that the Genesee run in the channel of 

 the Irondequoit, hut when that was filled with gravel and the region elevated, the Genesee was 

 turned westward and compelled to cut its present rocky bed like the Niagara. This phenomenon is 

 not rare, hut is many times repeated in this State. See notes 31, 38, 39 and 110. 



36. Rochester. See Genesee Falls out of the car windows on north side at the east end of the 

 station house. The gulf of the Genesee River, from Rochester to Charlotte, is remarkable for the 

 striking example of erosion which it exhibits. The distance is seven miles, in which the river forms 

 three cataracts over three distinct formations, the Medina sandstone the lowest, 84 feet fall; the Clin- 

 ton 25 feet, one and three-fourth miles below, and the Niagara group 96 feet fall, close to the railroad 

 bridge. It is evidently the different hardness of the groups or their varying facility of decomposi- 

 tion that have produced these falls. These three falls at first were but one, and at this time the 

 lower ones are gaining probably on the tipper one and the time may come when they will unite again. 



37. The 5 a. Medina formation is named after this place. 



38. At Lockport is a repetition of the Rochester and Niagara Falls ravine in the Niagara limestone 

 and shales here crossed by the railroad on a high bridge. Here too, a mile west of the city, yon can 

 see on the north side of the railroad an old, dry channel from which the stream was diverted by the 

 drift, corresponding to the Irondequoit at Rochester and St. David's at Niagara Falls. There is 

 another of these dry, old channels at Oak Orchard. 



39. Niagara Falls are six and a half miles south from lake Ontario at Lewiston, and the whole 

 distance the river runs in a gulf, which, at the falls, is 160 feet, and at Lewiston 300 feet deep and 



peared beneath the bed of the river, the falls being now in the Niagara group entirely, the shale lying 

 beneath the limestone. At the whirlpool, a little more than three miles below the falls, on the west 

 bank of the river, the continuity of the rock forming the bank is interrupted by a deep ravine filled 

 with drift material. This ravine may be traced two miles in a northwest direction, and from thence 

 another depression can be followed to Lake Ontario at St. David's four miles west of Queenstown. 

 When the ravine to St. David's was blocked up by drift materials the stream would be forced to 



