526 TEE POPULAR SCIENCE MONTHLY 



cultivated; the correlative branches are the Forest Service and the 

 Bureau of Plant Industry. The fourth pertains to the fauna, both 

 wild and domesticated, correlative respectively with the Biological 

 Survey and the Bureau of Animal Industry, together with the ancil- 

 lary insect life, correlative with the Bureau of Entomology. Adjunct 

 lines of work pertain to certain molecular relations, treated in the 

 Bureau of Chemistry and the Office of Public Eoads; to quantitative 

 or economic relations, treated in the Bureau of Statistics; and to 

 ecologic relations, treated largely in the Office of Experiment Sta- 

 tions. In each line the primary purpose is to discover facts and re- 

 lations connected with development or growth; the secondary purpose 

 is to redirect and control the course of natural development, and the 

 ultimate purpose is to progressively artificialize the earth with its life 

 and growth for the benefit of men and nations. In every line the 

 constant effort is to increase the efficiency of the better and to either 

 improve or eliminate the worse, and this in the light of all knowledge 

 and the exercise of all natural and human power. 



The immediate basis of life and growth on the earth is the soil; 

 it yields substance for the flora, which in turn sustains the fauna. At 

 the same time it is itself derived from cruder earth-matter largely by 

 the action of plants and animals, and its chief elements of fertility 

 (such as nitrates and potassates and phosphates) are organic deriva- 

 tives. Thus the primary law of the soil is cumulative enrichment 

 through interaction with floras and faunas ; to this law it has normally 

 conformed throughout the geologic ages; and the primary duty of 

 the soil specialist is to accelerate and intensify the natural progress, 

 and thereby to increase soil efficiency. Now the efficiency of soils de- 

 pends wholly on the associated water and air (unless indeed these be 

 considered integral parts of the soil), of which the former especially 

 maintains a sort of circulation, dissolving earth-salts, conveying plant- 

 food into and through the circulatory systems of the living and grow- 

 ing plants, and carrying the acids of growth and decay back to the 

 earth-matter to hasten its solution — so that the active agency or prin- 

 ciple of soil efficiency is the soil water. The normal processes are 

 sometimes interrupted or impeded by abnormalities: Certain organic 

 derivatives are excretory, and poisonous to the plants yielding them 

 and sometimes to others ; climatal and other natural conditions in con- 

 nection with cultural changes sometimes disturb the circulation of 

 soil water, or permit surface erosion and leaching to impoverish or 

 even completely remove the soil; and unsuitable plants sometimes 

 gain such foothold as to exclude organisms better adapted to normal 

 enrichment of the soil. Accordingly, the soil work comprises (1) 

 examination and classification of soils with respect to materials and 

 potentialities; (2) determination of the soil water and its movements 



