532 NEW YORK STATE MUSEUM 



The lowest beds, 125-Bl, of ilu' sandstone are at the Ellis 

 dam on the Saranac river about 1 mile above Cadyville, from 

 which point the sandstone is exposed at intervals down the 

 river for a distance of 2 miles to a point below the mill at 

 Kent Falls, where the hij^hest layer, 125-A13, of the Potsdam 

 iTthis section is seen dipping into the river. Below this latter 

 point the next outcrop of rock is of lower Beekmantown horizon, 

 12T-B1 to 3, at Treadwell's mill, 5 miles down the river. The 

 intervening space of 5 miles is occupied by drift deposits and 

 it is impossible to determine how much of the area is under- 

 lain by Potsdam sandstone and how much by the Beekman- 

 town beds. Still farther down the river, 2i miles, the Chazy 

 limestone, 127-A4, outcrops in the river bed with the same gen- 

 eral easterly dip. A short distance beyond the Chazy outcrops 

 the Trenton limestone appears in the stream and continues to 

 the lake shore. Throughout the entire section the strike and 

 dip has little variation; the strike changing from N 15' W to 

 N 15° E, and the dip from 5° to 10^ degrees easterly. There is 

 no evidence of faulting to increase the apparent thickness of 

 the deposits by duplication of beds. Computing from the 

 length of section, strike and dip, and difference in altitude 

 between the exposure of lowest layer and that of highest layer, 

 we obtain from the Potsdam an estimated thickness of 1150 

 feet, of which amount the upper 350 feet is fossiliferous. 



The lower portions of the formation as seen in this section 

 are of light color; generally gray, with variations to yellowish 

 and bluish gray and occasionally pink tints. The material is 

 quartz sand, well cemented with silicious cement, the grains 

 being both angular and somewhat rounded and varying in size 

 from i-2mm, with grains of 4 mm diameter on the surfaces 

 of some layers. Many layers contain a considerable admixture 

 of small grains of partly kaolinized feldspar. The layers vary 

 in thickness from 6-24 inches and are as a rule quite compact. 

 Ril»ple-marks are common on the surfaces of beds and cross- 

 bedding is seen in nearly all layers. A few layers have thin 

 pebbles of shaly material on their upper surfaces, but no 



