1995) TRANSEAU—BOGS OF THE HURON RIVER VALLEY 353 
note that a large part of the surface drained by the Huron and its 
tributaries, before it makes the great bend to the southeast below 
Portage lake, is made up of sand and gravel, composing and accom- 
panying the Saginaw-Erie interlobate moraine. It is a region of 
steep hills, with occasional dry plains, everywhere penetrated by 
lakes and swamps. 
The country which the river next crosses, beyond the great bend, 
for a distance of 20 miles (32*™) is composed of glacial till plains 
and clay moraines—a belt extending NE-SW, approximately parallel 
to the interlobate moraine. Here, although the hills are well marked, 
the slopes are more gradual and the basins broader. The river 
8 bordered by banks several feet in height, and seldom attains a 
width of x 50 feet (5o™). 
The last 30 miles (50‘™) of the Huron River traverses a meander- 
ing course sunken from 50 feet (15™) at Ypsilanti to 25 feet (7-5™) 
at Rockwood below the surface of a glacial lake plain sloping gently 
‘outheastward from the morainic belt just described, to the western 
shore of Lake Erie. The soil is here composed of sand, sandy loam, 
and—in the vicinity of the lake—clay; the only topographic features 
aside from the sunken water courses being the several beach ridges 
and dunes marking the successive stages in the lowering of the glacial 
lakes, forerunners of the present Lake Erie. 
There are, then, three natural divisions of the Huron drainage 
ah (1) the loose-textured rough interlobate moraine; (2) the 
¥ Morainic belt lying to the southeast of it; (3) and the low-lying 
8 extending to Lake Erie. Each implies important differences 
© Way of bog formation and provides edaphic factors which 
‘‘tmine to a large extent the nature of the dominant forest covering- 
PHYSIOGRAPHIC HISTORY. 
The history of these topographic features is for the most part 
bo : 
Hite "Pp with the retreat of the ice at the close of the last (Wisconsin) 
Mick “poch. A topographic map of the region lying between Lakes 
of toy and Erie shows that the morainic hills so characteristic 
won basin are part of a belt of similar physiography _ 
(fig. : cog Indiana well up into the “thumb” of lower 7 — 
* 2). This belt of glacial deposits is directly connected — 
