40 MICHIGAN SURVEY, 1908. 



field the most conspicuous features of this imperfect drainage are tlie 

 vast strips of s-sx-amp land found in the valleys and bordering the lakes 

 and streams. -Tlie rock bound character of the basins and the south- 

 ward tilting of the surface must greatlj' influence the form and extent 

 of these strips. The stream channels have not cut deeply but are largely 

 bordered by SAvamps, and the divides between many of them are very 

 low or may even be swanips, so that the drainage from either end of 

 a swamp may be into a different drainage line. Such imperfection of 

 the drainage means that evaporation rather than run off is the pro- 

 nounced feature, and this condition, combined with the insular loca- 

 tion, must gTeatly influence the relative humidity of the atmosphere. 

 The brownish waters of even the largest lake upon the island, Siskowit, 

 54 feet above Lake Superior, clearly shows the influence of the imper- 

 fect drainage and the extensive swamps of its drainage basin. 



The general character of the soil was indicated by Ives on the Linear 

 Survey map. This is as a rule shallow, the deeper being at the south- 

 western end (T. 64 N., R. 38 W.) and is characterized as "sandy loam 

 and stony, second rate sufiSciently deep for cultivation." At the head 

 of Siskowit Bay (T. 63 N., R. 37 W.) he records soil "stony, 2nd and 

 3rd rate land. Soil varies from a few inches to 3 or 4 feet in depth." 

 And near McCargoe Cove (T. 66 N., R. 35 W.) the soil is from 1 to 10 

 feet deep. The soil then in general may be said to be shallow, second 

 and third rate stony, sandy loam. In the swamps and valleys there 

 is a large amount of vegetable debris, although it is probable that this 

 is generally not deep. No bog lime or marl has been observed. Large 

 strips of the ridges are destitute of soil, especially those which have 

 been burned. No morainic materials were recognized, although the ice 

 overrode the island, and glacial boulders ai'e abundant in places, as 

 about the head of Washington Harbor. Dr. Lane writes me that there 

 is some till, "especially on the lee end near Washington Harbor." 



The origin of these soils appears to be relatively clear as there 

 are only a few possibilities available. Some of the pre-Glacial residual 

 soil may have been preserved but it has not been recognized. As above 

 mentioned there are some Glacial boulders and till. The post-Glacial 

 disintegration and decay of the rocks has been the most important 

 source, supplemented by organic remains, from the vegetation in par- 

 ticular. A fourth source is the lake deposits of sand and clay as the 

 waves have worked over the entire surface. These are best preserved 

 in what were once harbors or places protected from the waves. In 

 many localities the origin of the soil is diverse, several different pro- 

 cesses having contributed a part. 



From the above topogi'aphic relations it is seen that the flat-topped 

 ridges and depressions are due to the structure of the rock, the influence 

 of base leveling processes and probably also to faulting. The present 

 drainage is not suflBcient to explain the primary ridges and valleys; 

 these must therefore have been inherited from past conditions. The 

 present drainage is therefore consequent and in its infancy, hence 

 its imperfection. Prom a biological standpoint these facts are signifi- 

 cant because such conditions favor isolation of small streams, swamp 

 and lake habitats affect the relative humidity and produce a prominent 

 zonal and linear arrangement of the habitats along the ridges and 



