400 ANKUAL REPORT. 



that soils composed of the New and Old Red Marl and Sandstone 

 are generally better adapted for such fruit trees than any other in 

 Britain."' The clays are the soils in which the hop vine and the 

 cherry flourish. But here with us, through the agency of that 

 original Minnesota plow, the glacier, all these different types of 

 soil are mixed in utter confusion so that granites aind schists, sand- 

 stones, clays and limestones have been ground together and mingled 

 until all conspicuous characteristics, all individuality, has been 

 lost; color has been changed — the red of Lake Superior sandstone 

 has become paler while the blue of Cretaceous and Tertiary beds 

 has lost its tone and a dark color is given by the growth and trans- 

 formation of the vegetation of many years. Possibly the blacken- 

 ing of our prairie soils is owing to the frequent fires which sweep 

 over them. 



The great advantage of this interchange of conditions lies in the 

 wide diversity of crops it allows. Grasses and grains, fruit, flax, 

 and amber cane can be grown side by side, and a full yield of each 

 may be expected and that for many years without renewing the 

 soil. 



Yet plants will not take these mineral substances in the forms in 

 which we see them. 



The wheat plant will not stiffen and support its head with the 

 silica as we see it in the quartz crystal and in the quartz grains of 

 the granite, nor will the Indian corn take the phosphoric acid, the 

 potash and the magnesia so necessary for its perfection, in the form 

 in which those substances usually come to us; but decomposition, 

 solution and recom position are necessary, oftentimes, to bring them 

 into the proper service of the plant. As water is the universal sol- 

 vent, so powerful in its action that nothing known to man can 

 resist it, as it occurs everywhere in the air and upon the earth, as 

 well as within the firmest known rocks, it is natural to look to it 

 as the most powerful agent in the preparation of the rocks for the 

 growth of plants. 



The conditions which influence rainfall are numerous ; among 

 them proximity to the sea, altitude above its surface, level or bro- 

 ken condition of the face of the country and direction of the winds 

 furnish some of the principal causes which influence humidity and 

 its precipitation. 



Situated as Minnesota is, at a long distance from any mountain 

 system, and at an even greater distance from the sea, with a level 

 surface, and lying midway between the equator and the pule, the 

 rainfall cannot be great; nor can it under the same conditions be 

 strikingly small. 



