726 PROCEEDINGS OF THE OTTAWA MEETING 



of the Glacial period, is regarded as the chief cause of its vast accumulation 

 of snow and ice. The several stages of advance or growth of the ice-sheet, 

 interrupted by repeated recessions and readvances, are reviewed, as made 

 known by their series of till deposits, moraines, and stratified or modified drift. 

 Among the peculiar features of the upper Mississippi region are the large 

 driftless area lying mostly in Wisconsin, inclosed on all sides by the glacial 

 drift ; the loess, extensively developed west and south of that area ; and the 

 falls of Saint Anthony, which, with the gorge extending 8 miles downstream 

 to Fort Snelling, give an estimate of the duration of the post-Glacial period as 

 about 7,000 years. All the Mississippi valley above the mouth of the Ohio 

 is included in this study, but especial attention is directed to its higher part, 

 in Minnesota, from lake Itasca to lage Pepin. 



FISH REMAINS IN ORDOVICIAN IN BIGHORN MOUNTAINS, WYOMING, WITH A 

 RESUME OF ORDOVICIAN GEOLOGY OF TfJE NORTHWEST 



BY N. H. BARTON 



The paper is published as pages 541-566 of this volume. 



DISTRIBUTION OF DRUMLINS AND ITS BEARING ON THEIR ORIGIN 

 BY FRANK B. TAYLOR 



[Abstract] 



This paper presents a discussion of certain aspects of drumlins and drumlin 

 areas. They are considered with reference to their distribution in the regions 

 of Pleistocene glaciation ; in their relation to the larger elements of topography ; 

 to the marginal portions of the ice-sheet, and to the successive recessional 

 halts of the retreating ice-front. 



Drumlin areas occur typically in association with broad basins or lowlands, 

 such as our Great Lake basins and the lowlands of Scotland, Ireland, and 

 Scandinavia. Certain occurrences of drumlins which are apparent exceptions 

 to this rule are briefly considered. Drumlins are usually classed as forms 

 made under deep ice. The writer's studies indicate that while this is true, 

 there are certain facts which qualify such a statement. The relation of drum- 

 lins to the ice-margin, as shown by studies in Ontario and western Massa- 

 chusetts, seems to support the view that drumlins are submarginal forms, 

 made neither at the edge of the ice nor many scores of miles back under it, 

 but in a submarginal belt varying roughly from five to 20 miles in width and 

 beginning 1 to 5 miles back from the edge of the ice. The elongation of drum- 

 lins, or rather the ratio of the horizontal axes, is principally dependent upon 

 the velocity of ice movement during their formation. Drumlins are con- 

 spicuous by their absence in certain regions which seem in many ways favor- 

 able for their formation, namely, in Ohio, Indiana, Illinois, southern Michigan, 

 and parts of Ontario. No reason has been given for this peculiarity. Some 

 tentative suggestions are made bearing on this point. 



