528 TEE POPULAR SCIENCE MONTE LY 



Bureau. So the measurements are preparing the way for such control 

 of the rain that this gift of the heavens will be made an unmixed 

 benefit instead of a partial evil. Of the entire rainfall, only about a 

 third flows through rivers into the sea (chiefly in floods), while it is 

 estimated that fully half is evaporated, thereby returning to the air 

 to affect the weather and temper the climate; and measurements of 

 evaporation have begun, and will doubtless open means of exercising 

 some control over the water in the air, no less than that on the surface 

 and within the soil. Meantime it is estimated that less than a sixth 

 of the mean annual rainfall is actually utilized in life and growth and 

 other useful processes connected with the soil and its productions; and 

 it is becoming clear that larger and better uses of the elemental water 

 are possible through progressive redirection of the natural processes 

 and powers. In the beginning, men bowed to the storm and fled the 

 flood; later they predicted in order to seek shelter before trfe storm 

 arrived; now they seek control at least of the storm waters in order 

 that their volume and strength may be directed to welfare. 



The four elements interact through organisms, of which the sub- 

 stance is mainly from the soil and water and their products; their 

 circulatory medium and chief constituent is water, their force is from 

 the sun, and their functions are maintained by air. During the ages 

 the native flora adjusted itself to soil and earth-shaping agencies so 

 closely that each type produced a surface to fit its needs — forests de- 

 veloping deep and friable soils and steeper slopes, grasses developing 

 thinner soils and flatter slopes, and mosses producing spongy soils lin- 

 ing basins, each according to its kind and its capacity as conditioned 

 by climate. A quarter of the area of the United States was too arid to 

 sustain a full floral mantle, a third was wooded and more than a 

 third was grassed when settlement began; for wherever the water 

 supply suffices, vitality overspreads the surface and dominates the in- 

 organic earth. Without water, vitality fails; there is neither assimi- 

 lation nor germination, nor yet metabolism, in the absence of liquid, 

 while transpiration and respiration depend largely on the passage of 

 water from liquid to vapor. With water, the primarily organic circu- 

 lation extends from the plant to the soil below and the air above and 

 passes into still more complicated interrelations in animal bodies; and 

 the locus of most effective energizing on the planet is the infinitely 

 complex surface — the soil with its extensions in stem, leaf, flower, 

 fruit and other organic bodies — at which water is continually passing 

 from one form to another, absorbing or yielding latent heat, and 

 mechanically interacting with the sun in seizing and storing and trans- 

 ferring molecular action. This is the complex in which vitality attains 

 dominance over lower nature; and through it investigators are attain- 

 ing control over the vital powers for the welfare of men and nations. 



