12 TWELFTH ANNUAL REPORT. 



Lake Superior is 602 feet above the sea. The shore of this lake 

 is the lovvest land in Minnesota, while its highest land is the Mesabi 

 range, which, south of Vermilion lake and eastward, is found by 

 Prof. Winchell to exceed 2000 feet above sea-level. Itasca lake, 

 the head of the Mississippi, is about 1500 feet above the sea; and 

 this river at the southeast corner of Minnesota, 620 feet. Professor 

 Winchell estimates the average elevation of the entire state to be 

 approximately 1275 feet above the sea. 



Climate is the most important of the factors by which a flora is 

 modified, and this depends chiefly on geographic position, elevation 

 and contour, if a sufficiently large area is taken into account. The 

 warmest days of summer in Minnesota have a temperature of about 

 90° Fahrenheit, but such days are rare; and the greatest cold of 

 winter is — 30° or sometimes — 40°. The annual precipitation of 

 moisture as rain and snow is from 25 to 30 inches. It is distributed 

 somewhat equally throughout the year; damaging droughts or ex- 

 cessive rains seldom occur. In winter the snow in the south half 

 of the state is commonly about a foot deep during two or three 

 months; but farther north it attains an average depth of two or 

 three feet. 



The soil throughout the greater part of Minnesota consists of 

 glacial drift, a mixture of clay, sand, gravel and boulders, clay being 

 the principal ingredient, and boulders being usually infrequent. 

 This deposit has been gathered from diverse formations of granite 

 and gneiss, sandstone, limestone, and shales. Enriched at the sur- 

 face by the decay of vegetation through centuries, the black soil 

 on areas of the glacial drift has ordinarily a depth of one or two 

 feet, and is very fertile. Other varieties of soil are found in tracts 

 of gravel and sand, also generally quite fertile, which in many 

 places border the large rivers and spread widely upon the region 

 drained by the St. Croix and Crow Wing rivers and the upper Mis- 

 sissippi; in the lower alluvial bottomlands, which are mostly over- 

 flowed by the highest water of spring; on the cliffs of sandstone 

 and limestone which border the rivers in the southeast part of the 

 state; and on the hills of granite and crystalline schists north of 

 lake Superior. Each peculiarity of soil affords a congenial location 

 for plants which are absent or can not thrive elsewhere. 



Forest and Prairie. 



The most important and conspicuous contrast presented by the 

 vegetation covering different parts of Minnesota, is its division in 

 forest and prairie. Forest covers the northeastern two-thirds of 



