30 ■ Oil the Analysis of Soils. 



with water. With the calcareous matter it will form 

 gypsum, (a very insoluble salt) whilst with the mag- 

 nesia it will form Epsom salt, a salt of great solubility. 

 These salts are to be separated by priority of chrystal- 

 lization, and their respective weights being ascertained, 

 when deprived of the water of chrystallization, and 

 brought to an equal degi'ee of dryness, the quantity of 

 calcareous matter and magnesia in each may be ascer- 

 tained by Bergman's or Kirwan's tables of the pro- 

 portion of acid, alkali, earth, and water contained in dif- 

 ferent neutral salts. To those who are not provided 

 with such tables, it may suffice to say, that 



Acid Cal. Matter Water 

 TlOO parts of gypsum contain 48 34 18 



Acid Magnesia Water 

 100 parts ofEpsom salt contain 33 19 48 



As both clay and sand, in different proportions con- 

 stituting either a clayey or sandy soil, are distinguish- 

 iible by the sight and touch, there is no occasion for 

 giving any cliemical test, to prove their presence. The 

 proportion of the coarser parts of siliceous matter or 

 sand, in soils or mould, may be ascertained by washing. 

 The presence of vegetable or carbonaceous matter in 

 surface mould, when in any considerable proportion, is 

 apparent, either from its black colour, or from the ve. 

 getable matter, appearing in the soil in an undecayed 

 state. Chemical tests, in either of these Cases, are un- 

 necessary. When it may be requisite, however, to 

 ascertain the presence or proportion of it in clayey or 

 other soils, in which, from colour or extreme division 

 of parts, it is less apparent, it is to be done in one or 

 other of the following methods : 



