SOME COMPOUNDS OF COMMON ELEMENTS 165 



same fertilizer will not prepare the soil equally well for all 

 of them. The preparation of artificial fertilizers is a great 

 industry. 



The study of the needs of the soil and of crops has been 

 of great benefit to mankind. It is not the farmers alone 

 who are benefited, for the whole world depends on the suc- 

 cess of crops for its daily food. 



FIG. 81. EFFECT OF FERTILIZERS UPON CROPS 



This is a picture of potato harvesting in the state of Maine, which in 

 some parts has a natural soil adapted to the needs of the potato. The 

 average yield for the whole United, States is 92 bushels per acre. A .good 

 yield in " the potato county " (Aroostook, Maine) is 275 bushels per acre. 

 By the use of fertilizers well adapted to the soil and the crop, a yield of 462 

 bushels per acre was obtained from this field in the same " potato county." 



186. Poisons. A poison is a substance which produces 

 serious illness if taken into the body. An antidote is a sub- 

 stance given to remove the poison or overcome its effect. 

 The value of an emetic lies in its power to remove the poison 

 quickly from the stomach. In most cases of poisoning, good 

 antidotes are milk and raw eggs, especially the raw white of 



