l893-] UPHAM ESKERS NEAR ROCHESTER, N. Y. 187 



its of till are many intercalated layers of stratified sand, from i to 5 

 feet in thickness, often continuous along a distance of 100 feet or 

 more. These layers are mostly horizontal or only slightly inclined, 

 and no contortion nor evidence of erosion or tumultuous pushing for- 

 ward was observed. 



Beyond its intersection by the Genesee river, this ridge is the site 

 of the Rapids Cemetery, and thence it extends nearly due west two 

 miles along or close to Brooks avenue. It rises by usually gentle 

 slopes 30 to 40 feet above the land on its south and north sides, and 

 has a width of 25 to 50 rods, being often quite irregular in contour, 

 which with its clayey soil and occasional boulders, gives it a morainic 

 aspect. Where it is cut by the Buffalo, Rochester & Pittsburgh rail- 

 road, nearly two miles west of the river and between an eighth and a 

 third of a mile north of Brooks avenue, several recent excavations 

 showed about half of its material to be till, and the remainder very 

 compact stratified sand. These unlike deposits are irregularly accu- 

 mulated together, but no interblending was seen. The till has no 

 marks of water action, and the sand is free from boulders or gravel, 

 and is horizontally bedded or nearly so, being sometimes 5 to 15 feet 

 thick with an exposed extent of fully 100 feet. 



Relationship to the surrounding Country. — Throughout the city of 

 Rochester, excepting the Pinnacle hills and the gorge of the Genesee 

 below its falls, the surface is nearly a plain, with slight descent toward 

 Lake Ontario. The underlying Niagara and Clinton formations are 

 covered generally with only 10 to 20 feet of drift, which is mainly till 

 and in small tracts stratified clay or sand and fine gravel. North- 

 ward from Rochester, the surface in Irondequoit and Greece town- 

 hips declines with a gradual slope 200 to 250 feet in the distance of 

 5 to 7 miles to Lake Ontario. 



The fjord-like Irondequoit bay, lying between Irondequoit town- 

 ship on the west and Webster and Penfield on the east, stretches about 

 five miles southward from Lake Ontario, with a width varying from 

 one mile to a half mile, bordered by cliffs 100 to 200 feet high, which 

 rise to the general plain on each side. The maximum depth of Iron- 

 dequoit bay is 80 feet, which must be added to the height of the bluffs 

 to give the total depth of the eroded valley ; and its southern end, 

 where the Irondequoit river flows into it, is about five miles east from 

 the center of Rochester. Before the Ice age the Genesee doubtless 

 entered the lake through this valley, probably leaving its present 

 course near the mouth of the Honeoye creek, flowing eastward, 

 through Bush township and the southern part of Mendon, and thence 

 northward along the Irondequoit river and bay. In the southeast 



