[ 102 ] 



1O,OOO parts of Wormwood - 730 



_ of Vetches - 275 



of Beans - - 200 



of Fumitory 790 



The earths found in plants are four : silica or 

 the earth of flints, alumina or pure clay, lime and 

 magnesia. They are procured by incineration. The 

 lime is usually combined with carbonic acid. This 

 substance and silica are much more common in the 

 vegetable kingdom than magnesia, and magnesia more 

 common than alumina. The earths form a principal 

 part of the matter insoluble in water, afforded by the 

 ashes of plants. The silica is known by not being 

 dissolved by acids ; the calcareous earth, unless the 

 ashes have been very intensely ignited, dissolves with 

 effervescence in muriatic acid. Magnesia forms a solu- 

 ble and crystallizable salt, and lime, a difficultly solu- 

 ble one with sulphuric acid. Alumina is distinguished 

 from the other earths, by being acted upon very slowly 

 by acids ; and in forming salts very soluble in water, 

 and difficult of crystallization with them. 



The earths appear to be compounds of the pecu- 

 liar metals mentioned page 48 and oxygene, one pro- 

 portion of each. 



The earths afforded by plants are applied to no 

 uses of common life ; and there are few cases in 

 which the knowledge of their nature can be of impor- 

 tance, or afford interest to the farmer. 



The only metallic oxides found in plants, are those 

 of iron and manganesum : they are detected in the 



