STATE HORTICULTURAL SOCIETY. 897 



And the rock Ijound lakes of northeastern Minnesota, show alti- 

 tudes ranging irom 1400 to 1900 feet above the sea. 



The altitude of these lakes outlines pretty clearly the average 

 height above the sea of the surface of the state. As a rule, the 

 river valleys, as the Mississippi and Minnesota, are narrow and then 

 bluffs rise abruptly from them, hence they can form no large ele- 

 ment in striking an average of altitude; so too with the hill regions. 

 Some peaks of the Leaf Hills measure from 1,400 to 1,750 feet. The 

 Sawteeth peaks sometimes reach 2,000 feet or more. The 

 Mesabi probably in no case reaches 2,400 feet. A careful study 

 then of the foregoing altitudes, with an inspection of the charts of 

 altitude* lead to the conclusion that the state will average, not far 

 from 1,200 feet above the sea. Nearly all the prairie region of the 

 southern half of the state lies between 1,000 and 1,400 feet altitude, 

 and it .is only in the southern counties where the altitude exceeds 

 the last named figure. These highest portions of the state seem to 

 owe their height to the drift, a deposit which has several times 

 been mentioned in the foregoing pages. The Drift is a material 

 which has been deposited over nearly the entire state through the 

 agency of ice. These masses of ice, whatever may have been the 

 cause which produced them, whether it was the precession of the 

 equinoxes or the earth's inclination to the ecliptic, or the elevation 

 of the earth's crust to an extraordinary height, or whether it were 

 neither nor all of these, but rather, a hair or two, so to speak, 

 from the tail of Donnelly's comet, the results, as we see them today, 

 have a far-reaching effect upon the agriculture of our state. The 

 depth of the deposit is quite variable; it lies much thickei>over the 

 western half of the state than over the eabtern, where the under- 

 lying rock is frequently seen exposed along the streams and in the 

 hillsides; in the western part the rocks in place are almost never 

 seen except in the river valleys where running water has laid them 

 bare by removing a considerable thickness of overlying drift material. 

 Another means of estimating the thickness of this drift is furnished 

 in digging or boring wells. Frequently 150 feet or even more of 

 sand is passed through in the western part of the state in sinking 

 a well, while in the eastern half, 30 or 40 feet will bring one to the 

 limestone or granitic beds beneath. And there are two portions 

 of the state where no drift appears: these are Pigeon Point, in the 

 northeastern and a section in the southeastern corner of the 

 state, comprising Houston county and part of Winona and Fillmore 

 counties. Various conjectures have been offered for this phenome- 

 *rhe charts exhibited were prepared from data collated by Mr. Warren Upham. 



