Trans. N. Y. Ac. Set 78 Jan. 9, 



of 100 or 200 feet above the intervening valleys ; but the greater num- 

 ber are shorter and lower. Many of them were, when first cleared of 

 timber, very steep at their north ends, and on their east and west sides ; 

 but, with very rare exceptions, the southern slope is gradual. 



The large valleys are generally cup-shaped, the lip of the cup being 

 of drift material, as found by many sections observed and cited by the 

 writer. Such valleys were originally occupied by ponds or lakelets, now 

 obliterated by accumulations of muck or peat, though a few (Crusoe 

 lake. Duck lake, etc.,) still remain. 



The surface rocks of the region, are, beginning with the lowest, the 

 Medina Sandstone, Clinton Group, Niagara Group, and Salina Group. 

 The Medina occupies the surface for two or three miles south of On- 

 tario, lying at about the level of the lake in the vicinity of Great Sodus 

 and Port Bays ; while at Oswego Falls, twenty-four miles east, and at 

 the lower falls of the Genesee, fifty miles west, it rises 100 feet above 

 this level — indicating a shallow valley existing, previous to the ice 

 period, in the region occupied by the parallel hills. The Clinton and 

 Niagara Groups together occupy a tract of four or six or more miles 

 wide throughout the district, the latter forming the watershed between 

 the small streams flowing north directly, or south by a circuitous route 

 to Lake Ontario. From the Niagara Group to Cayuja and Seneca 

 lakes, the surface rock is the Salina, which here attains its greatest 

 breadth in the State. Above and to the south of the Salina, rise in 

 succession the Waterlime, Oriskany, Upper Helderberg and Hamilton, 

 in the latter of which are excavated the basins of Canandaigua, Seneca,. 

 Cayuga, Owasco, and Skaneateles lakes. The escarpment of the 

 Upper Helderberg limestones bends several miles to the south when 

 approaching Cayuga and Seneca lakes. This fact, taken in connection 

 with the great depth of these lakes — more than 400 and 600 feet re- 

 spectively—indicate that in this region w^as exerted the maximum of 

 glacial force in western New York. 



To return to the hills. These are covered to a greater or less extent 

 with bowlders of all sizes, up to three or four feet in diameter, com- 

 posed of Medina, crystalline, Hudson River, Niagara and Clinton rocks 

 — their relative proportions being in about the order named. Their 

 abundance diminishes from the Niagara outcrop southward. The sur- 

 ace soil, a sandy loam, shades downward into a non-bedded, tough clay, 

 generally red, filled with small, sub-angular, glaciated pebbles and 

 bowlders — in short, a typical bowlder clay, or till. 



The opinion held by the state geologists, forty years ago, that these 

 hills were formed by streams of water, is evidently erroneous, since there 

 are no accumulations of river gravel in the valleys, such as must have 

 remained had a broad sheet of drift suffered aqueous erosion. More- 



