30 On the Analysis of Soils, 



with water. With the calcareous matter it ^vill form 

 g}^psum, (a very insohible 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 degree 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 x)f 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 

 100 parts of g}-psum contain 48 34 18 



Acid Magnesia Water 

 100 parts of Epsom salt contain Z^ 19 48 



As both clay and sand, in different proportions con- 

 stituting either a clayey or sandy soil, are distinguish- 

 able by the ^ight and touch, there is no occasion for 

 giving any chemical 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 cai'bonaceous 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 i 



