Kemp — Geology of Essex County. 



597 



eastward. Roughly but carefully measured, the total thickness exposed above 

 the lake water is about seventy-five feet. Streaks of chert run through the 

 ledge, and coaly <>r asphaltic material appears in the cracks. Galcite pockets 

 are not lacking but, although I searched carefully over the ledges, I was 

 unable to find definite remains of organisms. Thin sections of the chert 

 merely exhibit a brown, nearly isotropic base with numerous rhombohedra 

 of calcite or dolomite scattered through it. A few opaque ones are 

 apparently limonite residues after original siderite. This outcrop was noted 

 by Charles E. Hall in his report on the Laurentian Iron-Ore mines of the 

 Adirondacks (Thirty-second Annual Report New York State Cabinet, p. 139), 

 who speaks of it as Chazy and as containing fossils. Fossils sufficientlv well 

 preserved would, of course, settle the stratigraphy at once, and I feel the 

 greatest hesitation in speaking of the ledges as Calciferous in opposition 

 to the earlier record. The resemblance is so close, however, to the 

 cherty magnesian limestones that are undoubtedly Calciferous and non- 

 fossiliferous on lake Champlain (as for instance just north of Port Henry, and 

 again just north of Crown Point on the Delaware and Hudson railway), and 

 the probability of Calciferous in this outlying district resting on Potsdam is 

 so great, that I leave the determination as stated, being ready to recall it if 

 the evidence of fossils should be against it. 



The interest of the exposure lies in the fact that it is the remotest 

 outlier yet found of the Palaeozoic sediments in the mountains. The 

 nearest outcrop is the little area of Potsdam sandstone, distant at least 

 ten miles in a direct line in the Putnam's pond valley of Ticonderoga 

 which, however, drains north through Penfield's pond in Crown Point 

 to lake Champlain. The actual divide at the head-waters is insignificant. 

 Down the Schroon and Hudson valleys the nearest exposure recorded is at 

 Hadley, about forty miles away. There is little doubt, however, that the 

 Hadley tongue formerly set back up the Hudson and Schroon valleys, 

 and that this little outlier is the only remnant, so far as we now know , 

 that is left. Hadley is given by the railway (see Macfarlane's Geological 

 Railway Guide, Second Edition, p. 118) at 60(5 feet, and Schroon lake 

 has lately been determined by the United States Geological Survey at 807 

 feet, so that the rise is now about 200 feet. The interesting point is 

 whether these modern valleys were depressions and embayments up which 

 the oceans set in Cambrian and Ordovician time ; or whether the early 

 Palaeozoic strata spread all across the crystallines and have only been 

 preserved in small in-faulted blocks, w r hose faulting is relatively modern. 



