GLACIAL LAKE ALGONQUIN. 



435 



north of Sault Ste. Marie and on St. Josephs Island. It seems certain also that some of Law- 

 son's numerous series on the north side of Lake Superior belong to this group. 



ALTITUDE. 



On Mackinac Island the strongest, most characteristic ridge of the Battlefield group — the 

 one to which the name was originally applied — lies in a plane about 90 feet below the highest 

 and 40 feet below the lowest of the upper Algonquin group. The altitudes of this beach as 

 determined by Goldthwait's spirit leveling are given in the following table. The measurement 

 at Sault Ste. Marie, Ontario, is by Mr. Leverett. 



Altitudes of Battlefield beaches on Mackinac Island and in vicinity . 



Sault Ste. Marie, Ontario 



Hessel, nearly 3 miles north 



Mackinac Island, battlefield 



Mackinac Island, northeast of Grand Hotel 



Mackinac Island, Benhams road 1 mile south of British Landing 



St. Ignace, 1 mile west of courthouse 



Mackinaw City, 3 miles south a 



Cross Village, "three-fourths of a mile east 



Beaver Island, west-central part 



Petoskey 



Burgess. 



Charlevoix 



Norwood 



Lake Michigan, July and August, 1907 



Altitude 



above sea 



level (in 



feet). 



Altitude 



below 



highest 



Algonquin 



(in feet). 



Altitude of other weaker 

 members of group (in feet) . 



Higher, 726, 729, 732, and 734. 



Lower, 703. 



Higher, 718; lower, 703. 



Lower, 693, 691. 

 Higher, 704, 705. 

 Higher, 690. 

 Higher, 668. 

 Higher, 676. 

 Lower, 652. 



a The highest beach on the line south from Mackinaw City to Carp Lake has an altitude of 757 feet near north side of Carp Lake. But it is 

 doubtul whether this is the highest Algonquin, for by comparison with other localities near by it seems about 10 feet too low. There is no higher 

 ground near this place. 



Gregory's report on his spirit leveling is not yet published, so that identification of the 

 principal Battlefield beach in places is as yet in some doubt, but it seems to be represented by 

 the following beaches : 1 



Location and altitudes of supposed Battlefield beaches. 



Altitude below 



highest 



Algonquin. 



Rogers 



Crawford's quarry. 



Posen 



Alpena, north 



Alpena, west 



Ossineke 



a Highest Algonquin not reported. 



The Battlefield group north of Sault Ste. Marie, Ontario, was found by Mr. Leverett to cover 

 a vertical interval of about 150 feet. Its upper and lower limits, however, have not been deter- 

 mined with entire certainty. 



One of the most important results of Goldthwait 's survey was the determination of the south- 

 ward convergence of the Battlefield beach with those above and below. It had been supposed 

 by some geologists, including the writer, that the Battlefield and Fort Brady beaches were each 

 due to a drop in lake level resulting from the opening of an outlet eastward to the Ottawa Valley. 

 This would place these beaches in planes passing southward below the Port Huron and Chicago 

 outlets and would mean that they pass southward below the Nipissing beach, which is of later 

 date and connects with the Port Huron outlet. Goldthwait's measurements, however, show that 

 the Battlefield beach converges with the highest Algonquin beach toward the south and less 

 rapidly with the lower beach of the upper Algonquin group and with the Fort Brady and Nipissing 



' Gregory, W. M., personal communication. 



