26 CHEMISTRY, GEOLOGY 



are- found in the inorganic part, or ashes, of our 

 commonly cultivated plants. But some plants 

 yield a much larger quantity of ashes than 

 others. One hundred pounds of dry hay will 

 yield, after burning, from eight to ten pounds of 

 ashes ; but the same weight of wheat will only 

 give between one arid two pounds of ashes. 



The proportions in which these substances are 

 found in the ashes of different plants differs very 

 much. The ashes of hay contain much more 

 lime than the ashes of wheat, and the wheat- 

 .ash contains more phosphoric acid than the hay. 



These facts are of the greatest practical im- 

 portance to the farmer, as we shall soon be able 

 to show our young friends; and many lands 

 have been ruined because the farmer neither 

 knew the nature of his soil nor the food his crops 

 consumed. 



THE FOOD OF PLANTS. 



Plants require constant supplies of food, to 

 enable them to live and grow ; without suitable 

 and abundant food, they soon die. 



Questions. Are all the substances described found in 

 the ashes of plants ? Do all plants leave the same weight of 

 ashes when burned ? Do the ashes of different plants differ 

 i in the proportion of these constituents ? Do plants need food ? 



