A RECONSTRUCTION OF WATER PLANES 471 



The lowest of them and two intermediate ones are especially promi- 

 nent. Forty feet below the Algonquins, and separated from them 

 by an interval in which there are no plainly developed beaches or 

 benches, is a beach of remarkable strength, called by Taylor the 

 "Battlefield beach," It was so named because of its conspicuous 

 development as a great ridge of cobblestones and gravel on the old 

 battlefield, on the north slope of the island. Below the Battlefield 

 beach another interval of 40 feet, unoccupied by any very persistent 

 beaches, leads down to the group known as the "Fort Brady beaches." 

 There are several of these ridges. Four of them fill a vertical interval 

 of 25 feet; below them are at least two others of which we have a dis- 

 tinct record. A little below the Fort Brady beaches is the "Nip- 

 issing shore line," one of very remarkable strength. It is probably 

 the most conspicuous of all the shore lines, and it is peculiar 

 in consisting usually of a bench and bluff rather than a beach ridge. 

 On Mackinac Island it stands 53 feet above Lake Huron, being 

 represented there, however, by a great deep-water barrier which 

 runs southwest from the Episcopal church. Below the Nipissing is 

 one stage of importance, marked by the "Algoma shore line." At 

 the Straits of Mackinac this stands about 25 feet above the lake. 



All these shore lines and groups of shore lines — the Algonquin 

 group. Battlefield beach, Fort Brady beaches, Nipissing shore line, 

 and Algoma shore line — can be traced southward from the Straits of 

 Mackinac, on this profile (PI. I), with certainty for at least twenty 

 miles, to Beaver Island, where they are all represented. But as they 

 are followed further southward the record of them is found to become 

 more and more imperfect and incomplete. The planes gradually 

 converge until the discrimination between them becomes difficult; 

 and what is more troublesome, in the development of cliffs at the lower 

 stages (especially the Nipissing and the present stage) many of the 

 higher beaches have been cut away and no record of them is left. 

 The exact position of the planes between the Algonquin and the 

 Nipissing, therefore, cannot be absolutely demonstrated, though a 

 reasonable amount of confidence is placed in the reconstruction here 

 given. In the case of the Nipissing shore line, however, there is no 

 uncertainty. Its exceptional strength and peculiar character make 

 it possible to follow this plane southward, down its gentle inclination 



