Trans. N. V. Ac. Set. 24 Nov. 



19. 



have found rounded fragments of the Potsdam sandstone, gneiss 

 enclosing graphite, and many kinds of granyte and gneiss, all of which 

 must have been transported from the Adirondack region and its 

 margin, as well as varieties of limestone which belong in the Helder- 

 berg range, near and southwest of Albany. 



In Orange County, Dr. Horton observed numerous blocks of labra- 

 dorite rock, rounded and very much worn, up to a weight of three or 

 four tons, which are identical with the noryte of Essex County. These 

 have also been traced all the way down the Great Valley to Pompton 

 Plains, in New Jersey. 



On the west of the Shawangunk range and of the Mamakating val- 

 ley, the rounded hills mainly consist of graywacke and flagstones of 

 Upper Devonian age, commonly capped by a thin stratum of conglo- 

 merate, which apparently belongs to the lower portion of the Catskill 

 formation. This rolling surface, rarely over 1,000 feet above the sea 

 near the Wallkill valley, rises gradually to an elevation of 2,000 to 

 2,500 feet to the northwestward, forming the high plateau of the centre 

 of the State. This surface is in general but thinly covered by drift, 

 and there is abundant opportunity everywhere to see that the sur- 

 face of the rock is thoroughly planed down, grooved, and scratched. 



The direction of the ice movement is shown by the following ob- 

 servations of Thompson and Mather, and which I have verified in the 

 vicinity of Monticello : 



Between Monticello and Bridgeville, com- 

 mon over all the ridges S. io°-i5° W. 



Bet. M. and Forrestburg, common on all 



elevated lands S. 10° W. 



Various parts of elevated lands in Sull. Co. 



(W. Thompson, Am. J. Sci., xxiii, 247) . . S. to S. 65° E. 

 Eastern declivity of mts. W. of Mamakating 



valley, furrows deep and distinct S. 78-80° W. 



South of preceding and directed toward low 



gap in Shawangunk mts S. 65° E. 



Quarries at Coeymans (800-1000 ft. high). . S. W. ? 

 W. Thompson found no grooves on the west side of the hills in 

 Sullivan County, and that the grooves often ran eastward along the 

 southern faces of the hills. 



Many large boulders are scattered over the hills, in all cases of the 

 slaty graywacke or of the conglomerate. One huge boulder of the 

 latter material, about 20-25 tons in weight, forms a rocking-stone at 

 a point 2i miles west of Monticello, on the Newburg and Cochecton 

 turnpike, at a height of about 1,400 feet above the sea. At Bridge- 

 ville on the Neversink, 4i miles east of Monticello, many such 



