Page:Popular Science Monthly Volume 68.djvu/214

 210 a depression which must have had its own small glacier on the waning of the ice. This small glacier has eaten back against the main ridge so as to leave the characteristic cirque with its precipitous head.

Near Mt. Marcy, in the Paradox Lake quadrangle, Dr. Ogilvie has noted very perfect and striking cases of small rock basins, which the writer has seen under her guidance. Each is occupied by a small mountain lake, and is a bowl produced by plucking and scoring. Giant kettles or potholes are to be seen in many places around the northern shores of Lake George, and more particularly two or three miles north of Hague, where they are locally called Indian Kettles. There must have been sinkholes in the ice sheet at these points, which are now above the level of the lake, and torrents poured into them until the moulin or mill was established.

While moraines and huge transported boulders are not altogether lacking, yet they favor special localities and, generally speaking, the boulders are of but moderate size. The Potsdam sandstone furnishes a material of special interest, since it can be easily recognized, can be referred to its parent ledges and is found all over the mountain tops.

The larger boulders are a quite marked feature to the west of Schroon Lake Post Office, and from a distance resemble small houses. One now cleft in twain near Hague, on Lake George, is fully thirty feet in diameter (Fig. 13). With the waning and retreat of the ice, lakes were impounded in not a few of the valleys and their surfaces reached to altitudes high above the present bottoms. Near Elizabethtown in the valley of the Boquet River, and in the Keene Valley along the east branch of the Ausable River the deltas formed by tributary streams are still very clearly preserved, cut in two as is usual by the downward erosion of the present stream. Ice must have largely formed the barriers. Other and usually small lakes, as has been noted by Professor C. H. Smyth, Jr., have reached the state of morasses or meadows, affording the so-called vlies of the early Dutch settlers.

With the waning of the great ice sheet the vegetation crept northward, covering moraines, sand-plains and hills with a coat of green. At first obviously Arctic in character as the little colonies of hardy plants still holding out on the mountain tops show, the flora and silva assumed gradually a more temperate aspect and prepared the Great North Woods to be the chief recreation ground for the people of New York and neighboring states.