THE PLANT AND THE SOIL. 17 



solved, but the water will feel and taste soapy. There is 

 evidently something soluble in wood ashes, and also some- 

 thing insoluble. If we take coal ashes instead of wood 

 ashes, we shall find that there is little or nothing soluble in the 

 coal ashes. It is evident, therefore, that wood ashes contain 

 much more soluble matter than coal ashes. This soluble 

 matter is food for plants. If we take a piece of limestone and 

 pour water upon.it we shall find that little or no change takes 

 place ; but if we use a little weak acid (even vinegar will have 

 some effect), we find that the limestone will dissolve. If, in- 

 stead of limestone, we take freshly-burnt lime quick-lime 

 we find that the water will take up some of the lime, as we can 

 tell by tasting it. 



We conclude that some substances are quickly soluble in 

 water, some slowly soluble, some insoluble, and that weak acids 

 will have the effect of dissolving some substances, such as lime- 

 stone and iron, that do not dissolve in water alone. 



Further, we find that water can dissolve only a certain 

 quantity of any substance that its power of dissolving is 

 limited ; and when the water evaporates or passes off into the 

 air, the substances, such as salt, sugar, and lime, that were 

 dissolved in it, reappear as salt, sugar, and lime. 



If we pour milk through a fine strainer, the milk all passes 

 through, and the dirt that was not dissolved remains behind. 

 If we stir up some hardwood ashes in a glass of water and 

 then pour it through a very fine strainer, we find the undis- 

 solved ashes remain behind, and the water that passes through 

 is soapy in taste. 



We conclude that the substances dissolved in the water go 

 along with the water wherever it passes in the liquid form. 



Take a clean unglazed earthen flower pot ; stop up the hole in the 

 bottom, fill it with water, and throw into the water a handful of salt. 

 Allow the pot to stand undisturl>ed. After a while a deposit will appear 

 on the outside of the pot. Taste it, it is salty. Explain. 



