GEOLOGY OF THE PENN YAN-HAMMONDSPORT QUADRANGLES 55 



downthrow toward the southeast of 9 feet. In the ravine at Crosby 

 the sandstones dip toward the southwest at the rate of 100 feet a 

 mile. 



The western side of the high ridge that separates Keuka lake and 

 Seneca lake shows at all exposures a strong dip toward the west, 

 that reaches in the north part of the quadrangles as far as the Naples 

 valley. The dip is reversed in part at least on the Seneca lake side 

 of the ridge as may be seen in the lower part of the Plum Creek 

 ravine below Himrods where the strata dip toward the east for nearly 

 a mile at the rate of 100 to 200 feet a mile. The Parrish limestone 

 is exposed in a series of outcrops on the west side of the Keuka lake 

 valley between Friend and Hammondsport, a distance of 13 miles 

 on a nearly north and south line. In the ravine at Friend the lime- 

 stone outcrops at 1095 feet A. T. and descends southward 45 feet or 

 18 feet a mile to the Belknap gully where it is 1050 feet A. T. This 

 latter exposure is 11 miles directly east of the one in the Lincoln 

 gully at Naples and 300 feet higher, an average descent toward the 

 west of 27 feet a mile. 



From Belknap gully to the road leading west from Gibson 

 Landing, which it crosses at 1005 feet A. T., the limestone descends 

 45 feet in 9 miles, a southward- dip of 5 feet a mile, and from this 

 outcrop south and a little west to Oak point, where it disappears 

 under the lake, it descends 296 feet in 6 miles, an average of 49 feet 

 a mile. Owing to the western dip it is above the water about i£ 

 miles farther south on the east side than on the west. 



From the place of its emergence on the east side of the lake to 

 its outcrop in the ravine on the east side opposite Urbana, the dis- 

 tance is 4 miles and the direction northeast. Between these points 

 the limestone rises 165 feet or 41 feet a mile. The place where the 

 limestone dips under the water opposite Hammondsport is 10^ 

 miles east and 14 miles south of the place where it is at the same 

 elevation, 709 feet A. T. at Naples. 



