THE IMPROVEMENT OF SOILS. 



47 



nishes the farmer with methods for preparing, in con- 

 centrated form, the very elements which are deficient 

 in an unproductive soil. Through the influence 

 of its teachings, the manufacture of fertilizers has 

 become one of the great industries of the world. 

 Substances in the highest degree offensive, injuri- 

 ous to health, and difficult to be gotten rid of, 

 have been converted into merchandise of great 

 value. 



101. The disposal of refuse matter, by putting it 

 to profitable use, is one of the greatest results ot 

 modern science. A portion at least of the sewage of 

 London, and other large cities of the world, is now 

 rendered harmless, and inoffensive, and even valua. 

 ble as an article of trade. A perfect system of agri- 

 culture requires that it should all be returned to the 

 soil whence it came, and serve as food for growing 

 crops. The indestructibility of matter, in connection 

 with the correlation and conservation of energy, pre- 

 sents nature as a grand system of mutually depen- 

 dent parts which move in a ceaseless round of univer- 

 sal harmony. It is for science to study the relation 

 of these parts, however vast or minute, and teach us 

 how to control their movements so as to promote 

 the interests of the human race. Much has been 

 done in this direction, while much remains to be 

 accomplished. 



102. All truly scientific methods of improvement 

 of soils are founded on observation and experiment 

 and are addressed to the reason and common sense 



