440 NEW YORK STATE MUSEUM 



across the axis. The modern divides in that region seem of 

 glacial origin, and our present knowledge does not suffice to de- 

 termine how much of the drainage west of the axis had been 

 captured in preglacial times. That the drainage of the Long lake 

 and Raquette lake valleys went out to the northwest in preglacial 

 times is exceedingly improbable, and it may well have gone east- 

 ward to the Hudson. 



The fact that the main axis of the region is to so large an 

 extent the modern watershed, is the strongest of the arguments 

 for its prominence having been given to it in comparatively recent 

 times. 



The northeastern streams, the Ausable, Saranac, Big Ohazy 

 and English rivers, flow in general northeast courses away from 

 the main axis. Faults clontrol them somewhat, and here the 

 direction of the main faults is also that of the consequent 

 stream flow. The upper Ausable and Saranac are, in part at 

 least, controlled by faults. In their lower courses all cut across 

 the strike of the Paleozoic r'ocksi. 



It is in the southeastern part of the region that the streams 

 show the most marked adaptation to the structures, as was noted 

 by Brigham on the publication of the first topographic sheets of 

 the region.^ The main streams here have n. to n.n.e. or s. to s.s.w. 

 courses and receive their main tributaries from the west. Such 

 Grenville belts as occur trend with the tributaries rather than 

 with the main streams, and the determining cause of location is- 

 obviously a structural one. Ogilvie argues that the faulting 

 was accompanied by block tilting toward the east, that the main 

 drainage lines are located along the faults, and that the tribu- 

 taries on opposite isides work against an abrupt fault cliff on the 

 one hand or down a. gently tilted slope on the other; that those 

 down the slope have a conspicuous advantage and have extended 

 their courses much farther back than those flowing in the 

 opposite direction.2 That the main streams follow the fault 

 lines, the writer quite agrees. And, if the faults downthrow to 

 the west, the rest necessarily follows. But, if they are normal 



^Am. Geol. 1898. 21 :219. 

 ^Jour. Geol. 10:408. 



