MacMillan : SHORES AT LAKE OF THE WOODS. 957 



which humus is the important component. It need scarcely be 

 said that these three groups are not named in an exclusive 

 manner, and that, as a matter of course, nitrogenous compo- 

 nents are found in the silicious and aluminous soils as well as 

 in the so-called nitrogenous. The notion is simply to indicate 

 certain preponderances and to give characteristic and appro- 

 priate terms to three important soil- types as found on the shore 

 areas at the Lake of the Woods. In this region, as has been 

 indicated above, certain varieties of soil are conspicuous rather 

 by their rarity or absence. For example, ferric, magnesic, 

 calcic, saline and alkaline soils are either wholly absent from 

 the region studied, or quite inconspicuous and unimportant. 

 Ferric soils are abundant, however, farther east, especially 

 upon the iron ranges; calcic and magnesic soils prevail in the 

 southern limestone regions of Minnesota, and saline, alkaline 

 or sodic and potassic soils are developed occasionally in west- 

 ern Minnesota. 



By no means all of the important factors in the classification 

 of shore areas have yet been recognized in the attempt in 

 brand. Besides the chemical and general physiographic 

 groups that have been defined there are a number of groups 

 which depend for their distinctive characters upon a mixture 

 of conditions rather difficult to bring together in an orderly 

 analysis. Possibly a series of groups blocked out with refer- 

 ence to the special conditions in each case involved may be 

 noted in serial order and thus the problems may be best ap- 

 preciated. 



I. Classification of shores with reference to illumination. 



A. Shores with stronger illumination. 



1. Shores facing S. E., S. or S. W. 



2. Shores of which the slope approaches a plane perpendicular to the 

 incident rays of sunlight. 



3. Shores not subjected to shadows from neighboring objects, such as 

 trees or adjacent shores. 



4. Shores upon which light is reflected by adjacent objects such as 

 mounds of white sand or smooth surfaces of light colored rock. 



B. Shores xoith tccaker illumination. 



1. Shores facing N. E., N. or N. W. 



2. Shores of which the slope varies from a plane perpendicular to the 

 incident rays of sunlight. , 



3. Shores subjected to periodic or permanent shadows from neighbor- 

 ing objects. 



4. Shores upon which light is not reflected by neighboring objects. 



