412 PROCEEDINGS OF WASHINGTON MEETING. 



developed and have been mapped by Brainerd and Seely.* They follow up the 

 Ticonderoga (locally called "Ti") river about half way to lake George, in whose 

 valley they do not appear again for some miles, or until the town of Bolton, on 

 the west shore, is reached, far beyond the limits of this little sketch map. The 

 sediments do appear, however, in the valley of Trout creek, to the west of the 

 outlet, in two small outliers. The dip is only 5 to 10 degrees, and the disturbance 

 is therefore slight. Presumably an old Cambrian channel was present in this 

 depression. 



Other Outliers 



Mention has just been made of the exposures at Bolton, on lake George. Pots- 

 dam and Ordovician are both present, as shown by the recent large geological map 

 of the state. At the south end of lake George, tongues of Ordovician strata stretch 

 in from the parent areas on the south. Attention should also be called to the re- 

 markable outlier of Paleozoics, showing Potsdam, Calciferous, Trenton, and Utica 

 beds at Wells or Wellstow r n, on the Sacondaga river. It was first discovered and 

 described by Vanuxem in 1842, and has lately been figured with many details by 

 N. H. Darton.f 



Conclusion 



The facts above set forth lead to the conclusion that the present large depres- 

 sions and lines of drainage were to a great degree outlined in Cambrian time. 

 They have been more or less modified by later faulting, but the vast erosion that 

 has taken place since the Cambrian, removing we know not how much of post- 

 Ordovician strata as well from the Adirondack region, has not sufficed to entirely 

 clear the valleys of the Cambrian and Ordovician sediments. Much of the later 

 excavation and removal of the sediments, especially of the Potsdam, was probably 

 done by the great ice-sheet, for Potsdam boulders are extraordinarily abundant 

 and widespread in the drift, even far into the mountains. Its abundance makes 

 the observer question if it has all been derived from the large exposures north and 

 east of the mountains. Glacial strise, so far as noted, are about north 50° to 60° east. 



Alternative Hypothesis 



If the above explanation of the Paleozoic outliers be not accepted, it is necessary 

 to assume that the Adirondack region was a peneplain in later Cambrian time, 

 and that the Cambrian-Ordovician sea spread over it, depositing a mantle of sedi- 

 ments, all of which have been removed except these small remnants, which have 

 been dropped by great faults and so preserved in the fault valleys. Although 

 faults, as has been often stated, are recognized by the writer as strong" factors in 

 the topography, the first conclusion seems to him much the more probable and 

 reasonable. 



Remarks were made upon the matter of the paper by M. R. Campbell, 

 H. P. Gushing, R. S. Tarr, F. D. Adams, A. C. Lane, and H. F. Reid. 



*Bull. Am. Mus. Nat. History, June 1890, vol. iii, p. 10. See also the writer's Report on Essex 

 County, already cited, p. 452. 



f Geology of the Mohawk Valley, Rept. of N. Y. State Geologist for 1893, p. 415 and p. 429. Mr 

 Darton also cites an outlier of Trenton limestone five miles south of Kattskill bay, on the east 

 side of lake George, p. 428. It lies against a fault. 



