REVIEWS 511 



It is considered a matter of doubt whether the time is expressible in tens of thousands 

 or in hundreds of thousands of years. 



Hitchcock, C. H. The Story of Niagara. Am. Antiquarian, Jan., 1901. 



Th(2 geological history is reviewed and the leading views concerning the falls 

 themselves are briefly presented. It is estimated that the time since water began fall- 

 ing over the Niagara escarpment is 18,918 years, distributed as follows: Erosion of 

 lower gorge below the cove, 6,844 years ; erosion of the cove section, 937 years ; 

 erosion of the gorge of the whirlpool rapids, 7,800 years ; erosion from the railroad 

 bridges to the existing cataract, 2,962 years. In addition to this 475 years is esti- 

 mated for the wearing out of the whirlpool basin. 



Martin, J. O. The Ontario Coast between Fairhaven and Sodiis Bays, New 

 York. Am, Geol., Vol. XXVII, pp. 331-334, with map, 1901. 



Describes the encroachment of the shore of Lake Ontario upon the drumlins and 

 the building of beaches between the drumlins with materials cut from them. The 

 shore has advanced at least one-fourth to one-half mile since the lake has had its pres- 

 ent level, and the rate of cutting varies from a few inches to ten feet a year. 



Ogilvie, I. H. Glacial Phenomena in the Adirondacks and the Champlain 



Valley. Jour. Geol., Vol. X, pp. 397-412, with map, 1902. 



Striae indicate that the Champlain-Hudson valley ice-lobe spread southwestward 

 into the Adirondacks, and there appears to be no change in direction resulting from 

 differences in altitude. There was very little scouring by the ice in the valleys of the 

 interior of the Adirondacks. Variations in the glaciation are separable into three 

 zones: (i) a zone of abundant striation, though variable bearing, along the Cham 

 plain valley; (2) a zone along the gneissic hills in which strise are not numerous, but 

 are uniform in bearing (northeast-southwest) ; (3) a zone among the high anorthosite 

 peaks where strise are lacking, but the mountain tops are smooth. 



The glacial deposits are largely of stratified material. A glacial lake which occu- 

 pied the Champlain valley has its shores marked by large delta accumulations at each 

 of several lake levels. This glacial lake was followed by an incursion of the sea, 

 which brought in a marine fauna. 



There appears to have been a glacial gathering ground in the interior of the 

 Adirondacks late in the Glacial epoch, and its local glaciers built up small moraines 

 across a few valleys. 



The drainage lines were begun far back in geologic time. The lakes are gener- 

 ally partially filled preglacial valleys, broadened perhaps by ice action. 



Salisbury, R. D. New York City Folio, Pleistocene Formations. Geol. 



Atlas of the United States, U. S. Geol. Survey, Folio No. 83, pp. 11-17, 



1902. 



The four fifteen-minute quadrangles in the New York City Folio are covered by 

 glacial deposits and glacial outwash except a small driftless tract of scarcely one 

 square mile near New Dorp on Staten Island. On this driftless tract is a gravel 

 deposit of late Pliocene or early Pleistocene age which is referred to the Beacon Hill 

 or Bridgeton formation. Gravel of the Pensauken formation is exposed under glacial 

 deposits in clay pits around Kreisherville, Staten Island, and by the waves in the cliff 



