THE SU1L AND ITS IMPROVEMENT. 93 



V. 



THE SOIL AND ITS IMPROVEMENT. * 



THE soil, the air, and the sun are the sources of all earthly 

 life. From the sun is obtained all energy or force; from 

 the soil and air the means of subsistence. Vegetable life,, 

 which is the original supporter of all animal life, draws from 

 these three sources. From the soil it obtains a small per cent 

 of its substance; from the air a larger per cent of substance, 

 and from the sun the power by which it is able to take up dead 

 minerals and invisible gases and work them up into all the use- 

 ful and beautiful forms of vegetable life. The sun pours down 

 its rays of life-giving energy unasked and unhelped. The air 

 brings daily to the plant unlimited supplies of food. It needs 

 no help from man ; he could not change it if he needed to ; it 

 is everywhere plentiful, everywhere alike in its supplies of 

 material. 



But the soil varies greatly. We have soils which seem to 

 contain all the material for the sustenance of vegetable life in 

 exhaustless abundance. We have soils which are either entirely 

 destitute of these substances, or else hold them in forms and 

 conditions which render them as unavailable as though in the 

 original rock, and we have soils occupying every shade of differ- 

 ence between these. 



The fertility of the soil is the measure of its capability for 

 supporting vegetable life, and on this depends the prosperity, 

 not of individuals alone, but of nations. The civilizations of 

 Egypt, Greece, and Rome had been impossible but for the won- 

 derful fertility of the soil they possessed. The remarkable 

 progress which has been made in the United States during the 

 first century of its existence has not been due merely to the 



* Contributed by R. S. THOMPSON, Author of Science in Fanning. 



