1902.] NATURAL SCIENCES OF PHILADELPHIA. 509 



holes by rapid currents of water carry in.i? the materials com- 

 nf ute7by means of swiftly whirling pebbhs qmte beyond he 

 hmis of sLh enormously large hollows. The unmensi y of the 

 currents required for such tren.endous action is wholly inadimsible 

 It is hardly necessary to discuss the extravagant idea that the 

 1 trs of L now buried valley escaped to the -^ through .ome 

 onginally deep subterranean crevice or channel, now l^>cWon farthe 

 ?han ever out of sight bv the glacial accunudations. The idea has 

 been resorted to merely'from the absence of any other thoroughly 

 plausibk explanation/ in view of the evident impossibility o 

 hoHowino- out a valley and carrying off the excavated ma enal 

 over T distant border two hundred feet higher than the bottom. 

 What seems, however, to bean extremely simple, natural and prob- 

 able solution of the problem has hitherto been appai^ntly allo- 

 Lther overlooked. The crumpling of the rock beds into folds by 

 fhe contraction of the earth's crust in cooling must necessarily 

 have been not a mere momentary movement, bu in general an 

 ex lemeTv slow one, continuing for many ages, perhaps, to be sure, 

 ^t^rmitteiUly, and moy probably slill be going on even in some 

 very ancient basins. A comparatively trivial amount of .uch 

 Ltion in the couple of hundred thousand years since glacia times 

 would be ample to effect the observed results. For, if the \\^o- 

 Z. basin had thereby been depressed by only the wholly insig- 

 nificant average amount of half a foot in a thousand years, and 

 Ue rock sadmes, or anticlinals, near Bloomsburg and Sunbury 

 elevated at the same rate, the whole observed residt would by this 

 time be accomplished, and the old glacial valley would be found 

 Tit is. a couple of hundred feet lower than those lowest present 

 outlets. A liberal allowance, too, can ensily be made to the 

 deg^^^^^^^ which those outlets have been eroded since the glac al 

 adion, and for the fact ihat they are not at the very ^ummi to the 

 anticlinals Yet the movement woidd be a trifling one. In fact 

 the obse'wl phenomena appear to be simply corroboration of wl^t 

 mi-ht with the utmost reason have been expected to occur; and the 

 rxSlanation is not by any means an arbitrary supposition of 

 ^^^^^^^^ or depression, conveniently imagined in order to 



suit facts apparently difficult to elucidate. 



June 10. 



Mr. Arthur Erwin Brown, Vice-President, in the Chair. 



Ten persons present. 



Prof Robert CoUett, of the University of Christiania, was dele- 

 gated to represent the Academy at the meeting commemorating the 

 services of Niels Henrik Abel to mathematical science. 



