3O NEW YORK STATE MUSEUM . 



the name of Heuvelton sandstone for it. It is, however, but one 

 out of several thick sandstones zones in the formation; there are 

 three or four others with a thickness of from 8 to 10 feet, which 

 may readily be mistaken for the other where outcrops are poor. 

 Nevertheless the Heuvelton is far the thickest and most prominent 

 of these sandstones, and forms a conspicuous bench wherever rock 

 outcrops are at all plentiful, so that it is readily mapped all across 

 the district, except for that part of its course across the Ogdens- 

 burg sheet northeast of Heuvelton, where heavy drift conceals all 

 rock. 



Above the 20 foot (Heuvelton) sandstone, beds of sandstone are 

 not so prominent and thick as they are below it, though they persist 

 to the summit of the formation. The chief constituent here, how- 

 ever, is massive beds of hard, blue, coarsely crystalline limestone, 

 full always of sand grains, and of irregular, black seams, or films, 

 of uncertain nature. 



Direct contacts of the Theresa with the Potsdam are to be seen 

 at several points along the river cliff above Holmes point and on 

 the south margin of the sheet 3 miles southwest of Brier Hill, and 

 also on the hillside above Black lake, 2 miles west of Kings 

 Corners, at the west edge of the Ogdensburg sheet. These show, 

 in every case, the thin-bedded, alternating sands and calcareous 

 beds of the typical Theresa, with a thickness of about 30 feet. In 

 the latter instance the Heuvelton sandstone directly follows these 

 thin beds. In the other sections a thickness of from 20 to 30 feet 

 of the more sandy, heavy beds lies between. In still other sections 

 this is increased to 40 feet or more. This considerable variation in 

 the thickness of the beds between the Potsdam and the Heuvelton, 

 together with the fact that, in the thinner sections, the beds which 

 are absent are the upper ones, suggests a break between the thin- 

 bedded zone and that which overlies ; and it is our belief that such 

 a break exists. But it is a difficult one to locate satisfactorily and, 

 in most sections, we are unable to fix it definitely. 



Of the many sections in these upper, sandy beds, containing the 

 Heuvelton sandstone, much the best and most complete one we 

 have seen is the one along the river road, as it climbs the hill just 

 out of Morristown going east. Recent road-making operations 

 there have resulted in exposing an almost continuous section in the 

 road gutter. Necessarily it will show less well as the years go by, 

 but just now it is a very satisfactory exhibition. As our work and 

 that of the road makers was in progress at the same time we had 



