PHYSIOGRAPHY OF THE ADIRONDACKS 209 



was near the Hundred Islands about midway of its length. One old 

 valley headed up in Northwest Bay, and the other probably did not 

 come much south of Sabbath Day Point. Faulting connected them, 

 however, and the damming by the drift of the old outlet to the south 

 at the head of Kattskill Bay and of the normal outlet to the north 

 into the Trout Brook Valley or possibly eastward into Lake Champlain 

 at Blairs bay, produced the present composite lake, with its pre- 

 cipitous mountainsides and wild rugged scenery. The old relations 

 are greatly obscured by the glacial drift. Schroon Lake is another 

 ponded and drowned river valley, with both a sluggish outlet and a 

 sluggish inlet, the former with wonderfully developed terraces on either 

 side, running like railway embankments as they mark old periods of 

 high water. The other notable series of lakes, like the Fulton Chain, 

 have been produced by the drift in the old valleys, which were the great 

 drainage lines before the glacial epoch. With moderate portages they 

 can be navigated long distances. 



Some of the smaller lakes are in fault valleys and not infrequently 

 are on the divides so as to be the sources of the streams. The Cascade 

 lakes (Fig. 7) between the Keene Valley and Lake Placid are good 

 illustrations. Although now two, they were once continuous and have 

 evidently been divided by a landslide. 



The Ice Invasion of the Glacial Epoch. — Coming after so long an 

 interval during which the Adirondack area was land the Labradorean 

 ice sheet possesses exceptional interest. All the scratches so far ob- 

 served and recorded point to a source on the northeast. The glacier 

 advanced from this quarter, and, as has been shown in some detail 

 by Dr. I. H. Ogilvie, rode over the highest mountains and apparently 

 filled the valleys with stagnant ice, since, except in the borders, scratches 

 are rare. In fact the Paleozoic strata, in the lower confines, where the 

 Champlain clays soon buried and preserved the scratches, are the 

 most prolific sources of observations. The hard Precambrian rocks 

 have mostly lost them by weathering. 



The ice sheet must have found the Adirondacks covered with a 

 heavy mantle of the products of decomposition. The long time dur- 

 ing which the mountains had been land could have had no other result 

 than this. It also found them of rugged topography much as now, 

 because if we believe or assume, as is reasonable, that the Cretaceous 

 peneplain was broken up into the flat-topped blocks by the preglacial 

 faulting, the region must have presented a very irregular barrier in the 

 pathway of the ice. The ice has left not a few characteristic topo- 

 graphic forms as the result of its action. Cirques appear on the flanks 

 of several of the higher mountains, as, for example, on the northwestern 

 side of Giant and the eastern side of Whiteface. Projections of the 

 ridge run out in each case at right-angles to the main axis, affording 



VOL. lxviii. — 14. 



