578 PROCEEDINGS OF THE PHILADELPHIA MEETING 



The Monominee area occupies at least 150 square miles, and contains many 

 hundred and probably several thousand drumlins. The drumlins are mostly of 

 the ridge-like type, are usually about 40 feet highland their longer axes trend 

 northeast and southwest. The till of which they are composed is reddish, sandy, 

 without lamination, and contains many flat slabs of limestone which are without 

 orderly arrangement. Boulders of native copper and of specular iron ore found in 

 the till indicate that it was deposited by a glacier moving from the northwest 

 toward the southeast. Striae, etcetera, on rock surfaces in the midst of the drum- 

 lins record an ice movement from the northeast toward the southwest. The 

 longer axes of the drumlins are not strictly parallel, but vary in trend from north 

 32 degrees east to north 55 degrees east. The rock on which the drumlins rest is 

 Trenton limestone and has a conspicuously even surface ; no knobs or crags are 

 present, such as might serve as nuclei for till accumulation. The larger drumlins 

 rise to a uniform height, and if the valleys and channels between them were filled 

 a nearly horizontal plain would be produced. The depressions separating the 

 drumlins are in many instances smooth- surfaced, concave troughs, and in one 

 example there is a well defined trench of this character, about 12 feet deep and 

 from 20 to 30 feet wide, about the northeast end of a small drumlin and extending 

 along its sides. The surfaces of the drumlins to a depth of some 12 to 18 inches 

 are composed of exceedingly fine, dust-like, loamy sand, which contains loose 

 stones and boulders. 



The drumlins are for the most part smooth-surfaced, half cigar-shaped hills of 

 the normal type, but in a few instances instructive irregularities are present. 

 Among these are a flattening of a portion of the normally elliptical ground plan, 

 as if a marginal portion of a well shaped drumlin had been removed by erosion, 

 leaving an abnormally steep slope ; deep transverse trenches at right angles to 

 their longer axes ; straight or curved trenches extending from their summits down 

 their sides ; irregular pits in their normally smooth surfaces ; and in one instance, 

 a terrace-like shelf with a convex longitudinal profile, parallel with the crest-line 

 of the drumlin on the side of which it occurs. 



In the valleys between the drumlins there are several eskers, which as a rule 

 are in a general way parallel with their longer axes, but in a few instances cross 

 their trend nearly at right angles. In one example an esker extends each way 

 from a transverse trench in a drumlin, and in a few instances eskers occur on the 

 tops of drumlins. 



From the evidence just summarized the conclusion is drawn that the drumlins 

 of the Menominee area were produced by ice erosion from a previously deposited 

 till sheet. This explanation is essentially in harmony with the theory of the origin 

 of drumlins advanced several years since by Professor Shaler. 



Attention was invited to the importance of ice erosion in shaping the topography 

 of glacial deposits in other regions. 



Lantern views in illustration of the papers on drumlins were then 

 shown and the papers discussed together. Remarks were made by W. M. 

 Davis, R. S. Tarr, G. C. Martin, and B. K. Emerson. 



