in the Cayuga Lake Region. 



231 



ton which was used for most readings. An average dip 

 of a little less than 1° (about 60') was thus established over 

 by far the greater part of the lake shore. The dip being 

 so gentle it is almost impossible to get accurate readings 

 even by sighting with a level clinometer on a telescope, 

 hence the impracticability of contact readings. 



The presence or absence of cliffs, as well as that of the 

 terraces, in some places so conspicuous, is due to the 



Fig. 2. — The Tully Limestone between Portland Pt. and Idlewood, east 

 shore of Cayuga Lake. The Tully is here shown capping the Hamilton with 

 the usual southerly dip. Though but 20' thick it forms a conspicuous terrace 

 with a corresponding dip to the south. 



nature of the formation exposed at a given locality, 

 whether hard or soft. The height of the cliffs and ter- 

 races, sometimes over 100' above the lake-level, is due to 

 the position of the two dominatingiy hard layers of the 

 district — the Tully limestone immediately overlying the 

 Hamilton shale, and the Encrinal bed of the Hamilton, 

 somewhat over 100' below. These two resistant layers 

 form waterfalls in all creeks which cross their outcrops, 

 the height of the fall being dependent upon the elevation 

 of the hard ledge. 



