THE BRAIN OF THE EARTH 



Not only must the soil be studied and tested 

 as to its chemical and physical properties, but 

 there must be artificial growing of plants in 

 the soils under artificial conditions. After re- 

 peated washings, a soil is prepared from which 

 has been taken every particle of nutriment for 

 plant-food. To make sterility absolute, the 

 soil is digested in a powerful acid and then the 

 acid is removed. The grain to be tested has 

 been sprouted either in water or warm sand, 

 and is then planted in the barren soil. 



Naturally it would be but a matter of a few 

 hours before the plant would droop and die 

 under these conditions, but the chemist is 

 ready with supplies of the four primary foods 

 with which to feed the plant in the sterile 

 soil, — now one food, now another, now two in 

 combination, now three ; now ceasing from all 

 food, and then, when the plant is at the point 

 of death, restoring it as if by a miracle by a 

 single meal, seized upon by the plant with all 

 the eagerness of one in the last days of starva- 

 tion. The plant is nourished, over-fed, under- 

 fed, or starved at will. There is a strange fas- 

 cination in these acts of the chemist, as when, 

 for example, he allows a plant to go on for 



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