436 PLEISTOCENE OF INDIANA AND MICHIGAN. 



beaches below. Thus it is not parallel to any of the other beaches, as it would be if the lake 

 had been lowered suddenly by the opening of a new outlet. 



Although Goldthwait's work does not carry the Battlefield and Fort Brady beaches south- 

 ward to an absolute union with any of the Algonquin beaches, it carries them so far in that direc- 

 tion that it leaves almost no doubt that they do in fact converge with the lowest member of the 

 upper group. This result seems to preclude the idea of outlets to the Ottawa Valley, except from 

 the last, lowest level of the Fort Brady beaches. In order that the Nipissing Great Lakes could 

 come into existence with full discharge eastward to the Ottawa Valley, there had to be at least a 

 slight chop from the lowest level that could discharge at Port Huron. But that drop was appar- 

 ently from the lowest Fort Brady to the original Nipissing which is now submerged in all the 

 region south of the isobase of North Bay. There is perhaps some doubt as yet as to whether the 

 lowest beach or two now classed as Fort Brady may in fact belong to this transition to the Nipis- 

 sing stage. Present facts seem against this view, but they are not conclusive. 



The facts seem to show that all but the very last and relatively small increment of the 

 uphft that began during Lake Algonquin turned on a hinge line without the intervention of a 

 drop of lake level by the opening of a lower outlet. Hence, the whole vertical interval from the 

 highest Algonquin down apparently to the lowest Fort Brady measures the vertical uplift during 

 Lake Algonquin. 



PORT BEADY GROUP OF ALGONQUIN BEACHES. 



DISTRIBUTION. 



At Fort Brady, in the southwest part of Sault Ste. Marie, Mr. Leverett found a cut bench 

 and cliff distinctly above the Nipissing and below anything that seemed likely to belong to the 

 Battlefield. He called it the Fort Brady beach. At other places this interval between the 

 Battlefield and Nipissing beaches was found to be occupied by a number of closely set, rather 

 light gravel ridges which seem to constitute a group by themselves. Where typically devel- 

 oped in the north several such beaches, separated by rather small vertical intervals generally 

 less than 10 feet, occupy an interval above the much stronger Nipissing beach and below the 

 Battlefield group, which seems to be distinctly set apart by a barren interval wider than usual. 



These beaches are persistent in all the northern region, but like the Battlefield beach, 

 they have nowhere been traced continuously for any considerable distance. 



At Mackinac Island they are not very well developed. Just east of the Grand Hotel they 

 occur as a group of very faint, short bars tying knolls of limestone. Four or five short ridges 

 belonging to this group lie in the woods above the Nipissing beach back of British Landing in 

 the northern part of the island and are considerably stronger than those near the Grand Hotel. 



At St. Ignace five f airly strong gravelly beach ridges which seem to belong to this group 

 are displayed in best development in the south part of the town. The highest two are strong 

 and beautifully formed ridges, and all are stronger than at any other place observed south of 

 Sault Ste. Marie. 



On the road north of Hessel two wave-cut benches between the Nipissing and the Battle- 

 field beaches probably belong to the Fort Brady group. Between Mackinaw City and Carp 

 Lake one strong, gravelly ridge and one faint one represent this group. Two or three ridges 

 of the same set were observed at several points between Mackinaw City and Cheboygan, and 

 two or three were observed between Mackinaw City and Cross Village. 



At nearly all of the many places where the Nipissing shore line is developed as a heavily 

 cut terrace with a high lake cliff behind it the Fort Brady beaches have been destroyed. This 

 is the case on the east and west sides of Mackinac Island, at Cross Village, at Harbor Springs, 

 and in the whole interval between these last two. At Petoskey two gravelly ridges appear to 

 stand hi the place of this group, but at Burgess they are cut away. 



The fullest development of Fort Brady beaches found is on Beaver Island. Seven or 

 eight ridges in the northeast part of this island seem to belong to the Fort Brady. The highest, 

 perhaps, belongs to the Battlefield group, leaving seven ridges, four of them strong and three 

 rather faintly developed. At Charlevoix there are two or three. At Norwood one ridge and 



