590 RECORD OF MEETINGS OF THE 



The Adirondacks cover some 10,000 square miles, and, ex- 

 cept for the White Mountains of New Hampshire and the Blue 

 Ridge of North Carolina, are the loftiest summits east of the 

 Black Hills of South Dakota. They are metamorphosed 

 Precambrian sediments and eruptives with a surrounding fringe 

 of Paleozoics, beginning with the Potsdam and ending with 

 the Utica, except for the Glacial drift. The eastern portion is 

 mountainous, the western a high plateau which slopes to Lake 

 Ontario. Three peaks exceed 5000 feet. The general profile 

 of the mountains is serrate, but there is great variety of shape. 



There are two contrasted types of valleys. One, doubtless 

 an instance of great geological antiquity, presents gentle slopes 

 and great maturity of form. Its members run east and west, and 

 north and south, and are occupied in some cases by the larger 

 lakes. 



The second type is more recent, and is due to faulting. The 

 valleys have on one or both sides precipitous escarpments. 

 The cliffs run northeast and southwest or northwest and south- 

 east. A third series of breaks running nearly due north is 

 also at times in evidence. The faults are most often the result 

 of differential movements causing even a marked sheeting of 

 the rocks. The faults run out into the Paleozoic areas, and 

 are shown with diagrammatic distinctness, where they have 

 been especially described by H. P. Cushing. 



The problem of the drainage is of especial interest. All 

 the waters go ultimately either to the Hudson or the St. Law- 

 rence. The courses of the large streams follow sometimes 

 the older type of valleys, sometimes the later. Barriers of 

 drift have often driven them from their old lines across low, 

 preglacial divides into new ones. The courses of the Hudson 

 and Sacondaga are particularly striking illustrations, each 

 exhibiting one or more marked bends to the eastward. 

 The courses of the two were described and discussed in some 

 detail. 



The different types of lakes were also described, including 

 the ponded river valleys from barriers of drift; the f ault~valleys ; 

 and the relations to the older type of depression. 



The nature of the ice invasion and its modifying effects were 



