CLIMATIC CHANGES IN THE PRAIRIE REGION 299 



over to the sun, performs its part in the wonderful metamorphosis that is taking 

 place. 



The roots of trees penetrate deeply into the reserve of moisture below the 

 surface of the earth, and constantly draw by capillary attraction a portion of it 

 which is exuded by the leaves, and the humidity of the air increases, as explained 

 above, and the temperature lowered. 



Shacht says: "In wooded countries the atmosphere is generally humid, 

 and rain and dew fertilize the soil. As the lightning-rod abstracts the electric 

 fluid from a stormy sky, so the forest abstracts to itself the rain from the clouds, 

 which in falling refreshes, not it alone, but extends its benefits to the neighboring 

 fields. * * The forest, presenting a considerable surface for evapora- 

 tion, gives to its own soil and to all the adjacent soil, an abundant and enliven- 

 ing dew There falls, it is true, less dew on a tall and thick wood than on the 

 surrounding meadows, which being more highly heated during the day by the 

 difference of insulation, cool with greater rapidity by radiation. But it must be 

 remarked, that this increased deposition of dew on the neighboring fields is 

 partly due to the forests themselves ■ for the dew saturated strata of air which 

 hover over the woods, descend in cool, calm evenings, like clouds, to the valley, 

 and in the morning beads of dew sparkle on the leaves of the grass and the 

 flowers of the fields. Forests, in a word, exert in the interior of continents an 

 influence like that of the sea on the climate of islands and of coasts ; both water 

 the soil, and thereby insure its fertility." 



This phenomenon of the condensation of dew is witnessed to-day on the 

 prairies beyond the Missouri as far as civilization has reached, and it appears to 

 be the result of causes analagous to those ascribed to the presence of forests ; 

 large areas of corn and immense fields of the other cereals, presenting the same 

 conditions, in a reduced ratio, however, as belts of woods ; at any rate, lands where 

 ten years ago the presence of dew could not be detected, now receive this bless- 

 ing in full measure, showing that the changes produced in the nature of the veg- 

 etation by the progress of civilization, the cultivation of forms superior to the 

 low grasses of the region in its primitiveness, are sufficient in increased surface 

 presented for evaporation to condense that which is thus extracted in the form of 

 dew, and thus save for the fertilization of the soil that which was once carrie<r 

 off by the atmosphere for the support of other regions. 



The absolutely cloudless skies, nights which knew not the refreshing in- 

 draught of the beaded dew, the wonderful pictures of the mirage, and the stifling 

 heat of the noon-day sun, were the peculiar characteristics of the climate of the 

 plains, as narrated in the reports of the early explorers, and to-day, in a certain 

 degree, these are the distinguishing features of a large portion of the interior of 

 the continent. But great changes have been wrought by the presence of man, 

 and his power to subordinate nature to his use is so mighty that even the ele- 

 ments seem to bow to his imperial will. 



The railroad was the potent avant courier of the wonderful civilization which 

 was so soon to follow in its wake, and although at first the hardy pioneer stepped 



