OCTOBEB 16, 1908] 



SCIENCE 



527 



surface. What offers a better repository for 

 this than the formation of elements of high 

 atomic weight which would then constitute 

 with the granite a surface layer of limited 

 thickness or a radioactive shell, as Dr. Becker 

 terms it? 



The whole paper is of extraordinarily sug- 

 gestive character, not only in the direction of 

 pure speculation, where but scanty data can 

 ever be gathered, but in offering several points 

 of contact with direct laboratory measure- 

 ment. 



Aethur L. Day 



SPECIAL ARTICLES 



PREGLACIAL DRAINAGE IN CENTRAL-WESTERN 

 NEW TORK^ 



The present drainage in central-western 

 New York is to the north. The principal 

 river is the Genesee, which traverses the en- 

 tire state from the Pennsylvania line, beyond 

 which it rises, to Lake Ontario. Its prin- 

 cipal tributary is the Canaseraga, which joins 

 it below Mount Morris. 



Throughout Allegany County, the Genesee 

 flows in a comparatively broad and open 

 valley with sloping drift-covered sides, and 

 with more or less drift-filling in its bottom. 

 In a few places the bed rock shows in the 

 river bed, indicating that the drift-filling in 



" Abstract of a paper presented before the New 

 York Academy of Sciences, Section of Geology 

 and Mineralogy, December 2, 1907. Read by title, 

 Albuquerque meeting of the Geological Society of 

 America, December 31, 1907. Only the main 

 points are here discussed; the complete paper, 

 which will appear shortly, will contain a detailed 

 discussion of the critical points of the region. 

 Since the manuscript of this paper was submitted 

 (January, 1908) Fairchild's discussion of the 

 drainage of this region (Bull. N. Y. State Mus. 

 118, January, 1908) and Spencer's "Evolution of 

 the Falls of Niagara" (Can. Geol. Survey) have 

 been received. In both the northward drainage 

 systems are defended. Fairchild treats all the 

 valleys as obsequent streams tributary to a west- 

 ward flowing Ontario River, while Spencer re- 

 asserts the existence of his Laurentian River. 

 These papers will be fully considered in the more 

 extended discussion of this subject now in prepa- 

 ration. 



the bottom of the valley is not deep. The 

 middle portion of the river lies in a series of 

 gorges, with a total length of about 20 miles. 

 The first of these gorges begins opposite Por- 

 tagevUle, and in it occurs the upper Portage 

 falls, about 70 feet high. Beyond this the 

 river passes across an ancient drift-filled 

 valley, the rock floor of which lies nearly at the 

 level of the present river below the upper falls. 

 A partial reexeavation of this valley has pro- 

 duced Glen Iris. Having crossed the ancient 

 valley on its rock bottom, the river drops a 

 further 100 feet, cutting a gorge into the 

 northeastern rock wall of the ancient valley to 

 a depth of 365 feet. A mile and a quarter 

 beyond this, the river again emerges into an 

 ancient drift-encumbered valley, into the rock 

 floor of which it has incised a narrow canyon. 

 Just before this ancient valley is reached, the 

 river makes a final drop of nearly a hundred 

 feet, in the lower falls. The Genesee is thus 

 incised at the lower falls about 250 feet below 

 the rock bottom of the ancient valley which it 

 crosses at Glen Iris. The distance between 

 the two points is a mile and a half. The 

 bottom of the gorge below the lower falls is 

 likewise nearly 200 feet below the rock bottom 

 of the ancient valley at that point. The two 

 ancient valleys thus crossed by the modern 

 stream have accordant bottoms. They are, 

 however, two distinct valleys which join op- 

 posite Portageville, where the system of 

 gorges begins. We will speak of these ancient 

 valleys as the Glen Iris Valley, and as the 

 Lower Falls Valley, respectively. The name 

 Upper Genesee Valley is given to the open 

 valley in which that river flows from its 

 source to Portageville. The Glen Iris Valley 

 and the Lower Palls Valley unite southward, 

 and from Portageville south are continued as 

 a single valley in the Upper Genesee Valley. 

 A third narrower drift-filled valley joins the 

 Upper Genesee Valley at this point, its mouth 

 being at the head of the first of the post- 

 glacial gorges. Thus three ancient valleys, 

 now drift filled, unite at Portageville, one 

 from the north (Lower Falls Valley) a second 

 from the northwest (Glen Iris Valley) and a 

 third from the west. These valleys are con- 



