LAKES. 237 



or rather commencement of Unadilla valley. It shows a handsome broad level flat, made up 

 in part of northern rolled stone, as is evident from some portions of the flat, and from exca- 

 vating below its surface. Its eastern side, towards the north, shows the Onondaga and Cor- 

 niferous limestone, the erosion of the range having extended to a lower level than at any 

 point farther east. 



These valleys, and these only are here noticed, because they are the only ones which 

 show, from the edge of the Helderberg range, the original bottom of the valley, with their 

 northern products ; no water having flowed over their northern part, since the change in the 

 relative heights of the north or original Mohawk and the south waters. The whole of the 

 valleys to the west of Bridgewater flats show the double inclined plane ; the present waters 

 dividing to the south of the Helderberg range, and flowing north and south in opposite direc- 

 tions. 



Lakes. 



The lakes to the south of the Helderberg range, are an important and interesting feature 

 of the district, furnishing facts to show that the excavation of those at the west end of the dis- 

 trict was anterior to the dip of the rocks, in all that part of the district which lies to the 

 southwest of the primary nucleus. Exclusive of Cayuga lake, there are six of note : Otsego, 

 Schuyler, Cazenovia, Otisco, Skaneateles, and Owasco ; the two first at the east end of the 

 district, shghtly inclining in direction to the west of south ; the three latter at the west end, 

 inclining to the east of south. These six lakes are entirely to the south of the limestone 

 range, being seated wholly in the lower part of the Erie division. Cayuga lake has the same 

 range with the three to the west, but extends about seven miles north of where the limestone 

 range is found on its border ; but it is no farther north than Skaneateles lake, owing to the 

 destruction of the range near Cayuga lake. The lakes to the east have their outlets to the 

 south ; those of the west, to the north. The whole of these lakes differ in no respect from 

 the long parallel north and south valleys of the same section, but in depth of water and appa- 

 rently greater depth of excavation. 



The great depth of several of the lakes, Skaneateles being 320 feet, Cayuga 396 feet ; their 

 outlets being shallow ; the exact accordance of their sides not admitting of faults ; the nature 

 of the mass in which they are seated, not permitting of subsidence without too extravagant a 

 supposition ; the south ends of the lakes to the west terminating in the higher rocks, the ele- 

 vation increasing south, render it impossible for the waters which excavated their basins to 

 have passed in that direction. 



There yet remains one supposition, which is, that of their excavation before the present 

 dip was given to their rocks ; the difference between the original horizontal and present posi- 

 tion of their rocks fully accounting for the greatest depth observed in the lakes. 



Should the excavation of the lakes have been made by a flow from the south to the north, 

 it comphcates the history of the surface of that part of the district, the rolled stones of north- 

 em origin showing a flow in the opposite direction. Whatever be the real facts as to the flow 



