NOKTH AMERICAN GEOLOGY. 191 



tion.s respecting the origin of the glacial epoch are discussed, and the 

 hy{)othesis that the regional refrigeration of the glacial time was 

 brought about by shifting of the terrestrial poles is favorably presented. 



2. In a paper on " iSTorth America in the Ice Period"* Kewberry dis- 

 cusses the iceberg theory and glacial climate, and states very forcibly 

 the objections to the former and to Whitney's theory of the latter. It 

 is shown that the iceberg theory is inapplicable to the mountainous 

 districts of the West, and can not be reconciled to such phenomena in 

 the I^ast as (I) the widely different altitudes of glaciation within short 

 distances; {2) the entire independence of the principal glacial features 

 of altitude in the vicinity- of the terminal moraine ; (3) the driftless area 

 of Wisconsin ; (4) the complete absence of marine shells in the inland 

 drift deposits; and (5) the characteristic effects of the erosion when 

 compared with glaciers now in existence. 



3. Brauner makes some very interesting observations on the relation 

 of topography to the glacial flow in the Wyoming and Lackawanna 

 valleys, Pennsylvania, a district of sharp relief and numerous rock 

 outcrops. Two systems of strife are found, one parallel to the general 

 southward slope of the country, and produced by the flow of the great 

 mass of ice in that direction, and another system determined entirely 

 by the local topography, and apparently due to the efiect of the latter 

 upon the ice sheet when it was greatly reduced in thickness.? 



The same writer | discusses the greatest elevation of glaciation in 

 northeastern Pennsylvania, finding that the glacier overrode peaks 

 2,200 feet in height, which White and Lewis considered islands above 

 the level of glaciation. These peaks are the Elk Mountains. Carefid 

 search has revealed unquestionable glacial striae on one of their sum- 

 mits. 



4. Britton§ finds driftless areas at a moderate height on the serpen- 

 tine hills of Statcn Island, a few miles north of the terminal moraine, 

 which indicate a thickness of the ice of less than 200 feet. 



5. In a paper on the geology of Cincinnati, 1| James gives some in- 

 teresting information on the local surface geology of that district, and, 

 in view of the absence of glacial drift from the tops of some of the hills, 

 doubts White's estimate that the glacial dam of t!ie Ohio stood 645 feet 

 above low water, as these hills are only 460 feet above at the highest 

 point. 



6. Salisbury discusses the distribution of drift copperin the Northwest. 

 As far as reported, it occurs over an area of nearly half a million square 

 miles, extending as far as 600 miles south, and several hundred miles 

 east and west, of Lake Superior. Fragments are especially plentiful at 



* Popular Science Moutbly, vol. 30, Nov., 1886, pp. 1-11. 



t Am. Phil. Soc. Proc, vol. 2!^, pp. 337-357. 



tAm. Jour. ScL, iii, vol. 32, pp. 362-3G6. 



^ Nat. Sci. Assoc, of Stateu Island, Proc, October, 1886. 



II Cincinnati Soc. Nat. Hiat., Jour., vol. 9, pp. 20-31 and 136-149. 



