2io POPULAR SCIENCE MONTHLY 



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 bar- 

 riers. 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 north- 

 ward, 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. 



