FOLDS IN THE APPALACHIAN SYSTEM 283 



exposures of the rock in the lake shore chffs on each side of the anti- 

 chnal axis, as far as the synchnal axes hmiting the arch make it 

 possible to measure accurately the total .height of the arch by noting 

 the thickness of the successive beds as they rise above the lake level.' 

 Measured in this way, the crest of the anticline is found to rise about 

 115 feet above the troughs of the synclines on each side. This 

 anticline therefore brings to view 115 feet of strata which are below 

 lake-level at the northern edge of the quadrangle. This includes 

 about 75 feet of typical Portage sandstones and shales, and some 

 forty feet of black and dark gray shales which represent the tran- 

 sition between the Portage and the Genesee, corresponding to the 

 Middlesex shales of Clarke and Luther. 



The north dips terminate at the synclinal axis crossing the lake on 

 the east side at the edge of the quadrangle north of Peach Orchard and 

 just north of Glenora on the west side. The axis of the Corbett's 

 Point syncline to the south of this fold crosses the lake just north 

 of Corbett's and Cottage Points, three miles south of the anticlinal 

 axis. The amount of the north and south dechnations of this fold 

 along Seneca Lake are practically the same, but its axis is a half- 

 mile nearer to the synclinal axis on the north than it is to the syn- 

 clinal axis on the south, so that the inclination of the north limb is 

 somewhat greater than that of the south limb. 



It is very probable that the anticline crossing Lake Cayuga in 

 the vicinity of Shurger Point, which has a maximum elevation of 235 

 feet on the east side and 160 feet on the west side,' is the northeastern 

 continuation of the Fir Tree Point anticline, but the continuity of the 

 two has not been verified by a study of the dips in intervening terri- 

 tory. Along Lake Cayuga, south of Shurger's Point south dips con- 

 tinue until the synchnal axis at Ithaca is reached, the rate of dip 

 being about no feet per mile. 



Watkin's anticline. — Six miles south of Fir Tree Point a second, 

 but much lower, fold crosses the south end of Lake Seneca. Its 

 axis crosses the lake just north of Watkins, six miles south of Fir 

 Tree Point. Continuing eastward by northeast, it crosses the Cayuga 

 Inlet valley in the southern edge of Ithaca. The maximum height 

 of the fold above the synchne on the north is about 35 feet. A band 



'^American Journal of Science, Vol. XXVI (1883), p. 304. 



