The area herein described is that part of New York State lying south of Lake Ontario, and west of longitude 76°. The dimensions of the area are, approximately, 95 miles north and south and 155 miles east and west, or nearly 15,000 square miles. The rocks are shales, sandstones, and limestones of the Upper Silurian and Devonian systems. The strike is nearly east and west, with a southward dip averaging perhaps 50 feet to the mile.