SEVENTH CHAPTER. 



THE MINERAL PLANT CONSTITUENTS LIME, 



SALT, SULPHUR, SODA, MAGNESIA, 



AND SILICON. 



T IME is a substance well-known to every reader. 

 Wlien freshly burnt, as quick lime or caustic 

 lime, it is a chemical combination of the metal cal- 

 cium with the gas oxygen having a great affinity 

 or passion for water and for carbonic acid. If ex- 

 posed to the air, it absorbs moisture, and after 

 awhile falls in the fine powder known as "air- slacked 

 lime." Afterwards it also absorbs carbonic acid 

 from its surroundings. We can often put this 

 passion of burnt lime for the two substances to good 

 use in various ways. We know that every 

 three pounds of it absorbs one pound of 

 water, and that it takes it wherever it finds it. 

 Undue or excessive dampness in cellars, tomato 

 forcing houses, etc., may be easily removed, or 

 greatly reduced, by placing boxes containing burnt 

 lime in such buildings or rooms; and cellars, mines, 

 wells, etc., can be cleared of the poisonous carbonic 

 acid gas, if any such exists in them, by a few hand- 

 fuls of freshly -slacked lime. 



Lime combined with carbonic acid exists in great 



