GLACIAL LAKE ALGONQUIN. 421 



Alpena. On the great sand plain west of Alpena the lower ridges of the upper group do not 

 appear continuously but may be represented by ridges that can be followed for short distances. 



From the spit north of the river the upper beach runs in moderate development 2 miles 

 southeast and turns northeast. At the turn and northeastward the upper ridge is massive and 

 is composed of coarse gravel and shingle. West of sec. 6 (T. 31 N., R. 8 E.) it is particularly 

 strong and has been excavated for ballast by the Detroit & Mackinac Railway. Some of the 

 lower members of the upper group are present but are weak. 



From the angle west of the corner, the upper ridge runs northeast nearly 3 miles and is well 

 developed most of the way. Where the road crosses it in east sec. 32 (T. 32 N., R. 8 E.) it is a 

 finely fonned shingle barrier rising 15 feet or more above the ground to the south. 



Northward from Alpena the drift is rather thin and limestone is exposed in many places. 

 The beaches contain a large proportion of shingle or flat, disklike limestone pebbles. The slope 

 below the Algonquin beach, especially below the lower members of the upper group, is very stony 

 most of the way from Alpena to Rogers. 



North and northeast of Alpena the narrow, thinly covered crest of the limestone ridge led to 

 the formation of a point and several islands in Lake Algonquin. On some of these the beaches 

 are finely formed gravel ridges, especially on one 4 miles northeast of Alpena mostly in the S. J 

 sec. 36 (T. 32 N., R. 8 E.), where an elongated oval barrier bar incloses lower ground. Several of 

 the lower ridges of the upper group are strongly developed on the lower slopes, especially the north 

 and east slopes of this bar. Slightly lower ground intervenes to the point of the mainland a mile 

 northwest, and some of the lower ridges are well developed on the north and south slopes of 

 the sag. 



Two miles east of the oval bar another small island, standing on the west shore of Grass 

 Lake, does not reach the upper level, but is finely crowned by one of the lower beaches and is 

 encircled by one or two fainter ones below. Two miles northeast of the oval bar a high ridge 

 runs northeast and southwest, two parts of which rise to the height of some of the lower beaches 

 of the upper group. The larger part lies east of the railroad spur from the cement mills and the 

 smaller one west of it. Both are surrounded near the top by gravelly beach ridges of moderate 

 strength and have two or three weaker ridges on their flanks. The trend of these two islands 

 produced passes close to the island at Grass Lake. The outlet of Long Lake flows close along 

 their north side, at the base of a rather steep descent of over 100 feet. Aneroid readings indicate 

 that the two islands fall a little short of the highest Algonquin level. 



From 5 miles north of Alpena the upper Algonquin beach runs 20 miles northwestward with 

 only trifling deviations from a straight line to a point 1 mile south of Crawford's quarry. The 

 upper beach is well developed through most of this distance and the lower members of the upper 

 group are well displayed in a number of places. Near the south end of Long Lake, about a mile 

 southwest of Summerville, the upper beach and some of the lower members are finely developed. 

 Wave action was apparently particularly effective here because the descent from the beaches to 

 Long Lake is quite steep and the water was deep close to shore. Four miles northeast of this 

 locality on the land between Long Lake and Lake Huron a high knoll appears to record at least 

 two of the upper Algonquin beaches, but does not reach the highest level. Along the west side 

 of Long Lake one of the lower beaches of the upper Algonquin group forms a fine bar a mile east 

 of the highest ridge. 



At the northwest end of Long Lake the beach is irregular and broken on account of the rough- 

 ness of the country but is well formed at most places. The upper beach runs west for 2 miles 

 from the lake and then turns sharply north. A mile north of the turn an island about a mile 

 long, apparently belonging to the highest Algonquin level, lies about half a mile east of the main 

 shore line. From its southeast end a gravelly spit runs southeast over half a mile and from its 

 northwest side a low bar runs northwest about 1£ miles to the mam beach. 



Northwestward the upper beach passes around the west side of Lake Augusta. From the 

 angle west of Long Lake to the northwest side of Lake Augusta, it is considerably weaker than 

 usual, apparently owing to the formation of a great gravel bar on a low, broad ridge which stands 

 about at the highest Algonquin level on the east side of the lake. This ridge forms the east side 



