30i: 



IJTDEX. 



Phosphurets, 



" action of air on, 



Pigeon dung, 



" '' value of, 

 Pine ashes, analysis of, 



" plains, lime and potash in. 

 Plants for food, . 

 '• product of, 



'* repay labor of cultivation, 

 " natural limit of, 

 " artiGcial " 

 " limits of, what determined by, 

 " laws of distribution of, 

 " irregularity of limits of, 

 " limits of grain bearing on mountains 

 " earthy parts of, 

 " not all contain the same elements, 

 " elements of, return to earth, , 

 " always contain salts and silicates, 

 " always form acids, 

 " galvanic action of, 

 " decomposing action of, 

 " animal principles in, 

 " " '• analysis of, 



Plaster of Paris, formation of, . 

 " " application of, 



" " action of. 



Ploughing in of crops, 



" " great fertilizing power of, 



" *• green, action of, 



" '* compared with dry, 



Polstorff, experiments of, . . 



Potash, silicate of, . . . 



** combining weight of, 

 •* solubility in water, 

 " caustic, 

 *' in granite, 

 " carbonate of, in ashes, 

 " may supply the place of lime, , 



