190 TRANSACTIONS OF THE [may 18, 
metamorphosed crystalline rocks, which valleys represent beyond 
question the old Pre-Cambrian river valleys which were filled 
with sediment by the encroaching sea of Potsdam and Ordovician 
times. Lake George is the largest example of this kind, and 
contains remnants of Potsdam sandstone and Trenton limestone 
in the southern portion. The valley of Trout Brook, which lies 
just west of Rogers’ Rock, at the north end of Lake George and 
is separated from it by a high intervening ridge of gneiss, con- 
tains two outliers of Potsdam sandstone of a few acres in ex- 
tent. In the valley of Putnam’s Pond, in the western part of 
Ticonderoga township, there is another outlier of Potsdam 
sandstone. Both these latter are shown on the map of Ticon- 
deroga which accompanies the speaker’s report on this region to 
Prof. James Hall, which report was published in 1895. Another 
isolated area of Calciferous limestone is found on Schroon Lake, 
under Schroon Lake Post Office. It is a few acres in extent 
and the exposed rock is about 75 feet thick. It is about 
850 feet above tide at its upper point. Down the lake and 
river valley it is nearly forty miles to the next Cambrian out- 
crop, which is below Hadley. The speaker also cited the little 
outlier on the Newton Mountain, near Wells, on the Sacondaga 
River, and the fact that the Cambrian and Ordovician sediments 
on the west side reach short distances into the areas of crystal- 
line rocks and along the river valleys. He stated that all the 
outliers on the east had a uniform northeasterly strike and a dip 
10 to 20 degrees to the northwest. He remarked that they occur 
in the valleys of streams which are now notably sluggish, and 
explained this slow movement by suggesting that these streams 
flow in Pre-Cambrian valleys, which were in that time reduced 
nearly to a base level. He referred this parallel strike and dip 
to the later faulting and tilting of the strata inthisregion. Re- 
marking upon the undoubted presence of faults in the development 
of the topography he emphasized the evidence that this early 
erosion acted long before the time of fossiliferous sediments. 
He added that the old river valleys had been in part determined 
by the presence of crystalline limestones. The paper was dis- 
cussed by Messrs. Dodge and Hovey. 
