476 JAMES WALTER GOLDTHWAIT 



as actually established. From this series of diagrams it may be seen 

 that (i) the "Algonquin" beach of the Michigan basin marks the 

 "two outlet" stage when the discharge was shared between the pass 

 at Port Huron and that at Kirkfield. Before it there had been a 

 "low-water" stage, adjusted to the Trent (i. e., Kirkfield) outlet 

 in its original low position; but earth movements had lifted the outlet, 

 and consequently the lake level south of it to the level of the Port 

 Huron pass. The records of this low water stage (southern continu- 

 ations of planes h and c) have been drowned in the Michigan and 

 Huron basins. The lower members of the group of Lake Algonquin 

 beaches, the Battlefield and Fort Brady beaches, represent successive 

 stages after the restoration of the Port Huron outlet (planes e and /). 

 Each seems to record a differential uplift in which the northern part 

 of the region was raised out of water, from a hinge near Onekama. 

 The Nipissing plane {h) represents, like the Algonquin, a " two-outlet " 

 stage, with the discharge divided between Port Huron and North 

 Bay. Previous to it the low Nipissing pass east of North Bay had 

 been opened and a second low water stage had occurred. The data 

 thus far collected seem to admit a possibility that this was a stage of 

 temporary marine submergence; but further careful studies and 

 more accurate measurements in that most critical field will be needed 

 before the truth is known. With repeated uplifts, the waters of the 

 Huron and Michigan basins rose from this low level, the "low water" 

 beaches were drowned (except north of the Nipissing pass), and the 

 Port Huron outlet was re-established. Since then the Nipissing 

 plane has been raised far out of water. The Algoma beach (i) seems 

 to mark the most important pause in this period of comparatively 

 recent uplift. 



