450 C. R. DRYER — FINGER LAKE REGION OF WESTERN NEW YORK 



Hamilton, and Genesee shales, its middle by the sandy shales of the 

 Portage group (Naples beds), and its southern by the sandstones and 

 shales of the Chemung. All except the Chemung sandstones are thin 

 bedded and friable rocks. The region is nearly all included in the Canan- 

 daigua, Naples, Honeoye, and Wayland quadrangles of the topographic 

 atlas of the United States. 



This region is not unknown to geologists. It has been studied by 

 James Hall, Chamberlin, and Fairchild. Each has given attention to 

 special features, and has recognized and solved some of the many prob- 

 lems in which it richly abounds, but no one has attempted a general 

 survey and correlation of data or made an exhaustive study of details 

 in any one group. Its complete history can not yet be written, but this 

 paper is offered as a contribution to that end. 



Valleys and Ridges 



The most conspicuous topographic features are the deep, narrow 

 south-north valleys and the broader ridges between. The principal 

 valleys are nearly straight, more than 1,000 feet deep, and from one-half 

 mile to two miles wide at the bottom. They attain their greatest depth 

 within a few miles of the head, and through three-fourths of their length 

 their floors are flat and have little or no slope. All are dammed at the 

 lower end by glacial drift, through which the outlet streams have cut 

 gorges. They present the same general characters as the larger Finger 

 Lake valleys to the east, but possess also some peculiarities, which make 

 them worthy of special study. 



The ridges present a general similarity of form, with a great variety 

 of detail. Their crests in cross profile are flat or gently rounded, but 

 in longitudinal profile are cut by shallow transverse passes into a series 

 of elongated domes, which often present a drumlinoid curve. 



Marrowback hill, on the west side of Hemlock valley, is 9 miles long 

 by about 3 miles wide. Its crest rises gently to a summit near the south 

 end, 1,920 feet above tide. It is cut off on the southwest by a diagonal 

 pass at a level near 1,300 feet. 



Bald hill, between Hemlock and Canadice valleys, is a symmetrical 

 and completely isolated ridge 6 miles long and 2 miles wide. Its form is 

 that of a perfect drumlin, with a summit at 1,840 feet near the south end. 



About the heads of Honeoye, Bristol, and Canandaigua valleys the 

 plateau is more thoroughly dissected, and presents many isolated domes 

 and peaks, which rise 300-600 feet above the surrounding valleys. The 

 surface of the plateau mass, 6 to 12 miles wide, between Honeoye and 

 Canandaigua valleys, is complicated by high-level north-south valleys, 

 connected by still higher passes. Between them massive domes rise to 



