36 SEVENTH REPORT. 



moraiae, just as the time required for tlie making of tlie Belmore beach 

 was enough for the making of the Port Huron moraine.* 



There are many evidences of re-advance of the ice front in other inter- 

 vals of tlie general glacial retreat. If, as seems to be the case, every so- 

 called ''recessional" moraine marks the climax of a re-advance and if there 

 was in each case so long a pause before the re-advance it seems plain 

 that the rate of the general glacial retreat was slower and the time it 

 occupied longer than some authors have supposed. 



Fort Wayne, Ind. 



DKUMLTN AREAS IX NORTHERN MICHIGAN. 



ISRAEL C. RUSSELI-. 



There are at least two regions in the Northern Peninsula of Michigan, 

 in which drumlins form the most conspicuous features of the topog- 

 raphy. One of these areas includes Les Cheneaux Islands and a part of 

 the adjacent mainland, on the north shore of Lake Huron; and the other 

 area is situated principally in Menominee County, to the Avest of Green 

 Bay. 



Les Cheneaux Islands area embraces about 70 square miles, the 

 numerous drumlins within it are of the elongate, ridge like type, are in 

 general about 40 feet high, and trend N. W. and S. E. The direction of 

 ice movement to which the drumlins are due, as recorded by striae, etc., 

 on rock surfaces, was from the N. W. towards the S. E. Many of the 

 drumlins are partially submerged in the water of Lake Huron and form 

 T^s Cheneaux Islands and the capes on the border of the adjacent main- 

 land; the conspicuous parallelism of the longer axes of the islands and 

 of the neighboring capes, is due to this cause. The drumlins are for the 

 most part below the horizon of the Nipissing beach, and have been 

 washed by lake waters so as to remove the greater part of the fine material 

 formerly present on their surfaces, and concentrate the stones and 

 boulders. 



The Menominee 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 high, and 

 their longer axes trend N. E. and S. W. The till of Avhich they are 

 composed is reddish, sandy, without laminaton, 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 N. W. toward the S. E. 

 Striae, etc., on rock surfaces in the midst of the drumlins, record an ice 

 movement from the N. E. toward the S. W. The longer axes of the drum- 

 lins are not strictly parallel, but vary in trend from N. 32° E. to N. 55° 

 E. The rocks 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 



*A11 these phases of the glacial retreat have been discussed in a previous paper. "Moraines of 

 Recession and their significance in glacial theory," Journal of Geology, Vol. V, No. 5, 1897. 



