Taylor — Highest Shore Line on Mackinac Island. 215 



feet or more above the lake. They have been cleared for 

 cultivation and they show those peculiarities of surface forma- 

 tion which characterize only an unmodified drift topography. 

 They are heavily drifted and their surfaces have those long, 

 graceful curves with upward convexities which are unerringly 

 attributed to the constructive action of the ice sheet, and 

 which are plainly not a product of any known destructive or 

 eroding agent. In case of greater submergence they would be 

 exposed, as the shore below is to-day, to the full force of the 

 west and northwest winds, and they could hardly escape the 

 eroding action of the waves. The modified course of Bear 

 Creek proves that during the formation of the Algonquin 

 beach at this point, and during the entire subsequent recession 

 of the waters down to their present level, the waves of the 

 west winds have played a strongly predominant part in the 

 modification of the shore. Below the Standard Oil Co.'s 

 station south of Petoskey, Bear Creek runs towards the north- 

 west and once entered the lake in that direction through a 

 narrow gorge. But its present course turns abruptly from 

 northwest to northeast where its banks are about 90 to 100 feet 

 above the lake. From this point it flows about half a mile to 

 its mouth in a course nearly parallel with the present shore, 

 and descends quite rapidly. There are good exposures in the 

 banks at the bend and they show deep sections of character- 

 istic beach material — rounded pebbles, gravel and sand — up to 

 about 90 feet elevation. The position of this material shows that 

 at the time of the Algonquin submergence the eastward littoral 

 transportation was so great that it forced the stream to turn 

 aside in the direction of the movement, and the continuation 

 of the stream in the same modified course ever since shows that 

 the same disturbing element has acted continuously at lower 

 levels. The shortness of the rock gorge below the bend indi- 

 cates a comparatively recent date for the change. Many lakes 

 along this shore have been partly formed by littoral dams of 

 Algonquin or later age. 



But in respect to exposure to wave action, Mackinac Island 

 seems to me to be a test case. For its geographical position is 

 such that in the event of a general submergence of that region 

 to or beyond the depth indicated by the Algonquin beach, it 

 would stand alone in a wide expanse of water. The nearest 

 mainland would then be about 30 miles to the south and the 

 nearest islands about 20 miles to the north and southwest. In 

 all other directions open water would stretch away 100 to 200 

 miles. From Traverse City to Mackinac Island and at least 25 

 miles farther north, the plane of wave erosion appears to have 

 acted at every horizon up to the level of the Algonquin beach. 

 But above that plane there is no evidence of such action ; at 



