AGRICULTURE WITH CHEMISTRY. 



157 



thoronn;hly. The dropping in of the dried mould should 

 be continued until the complete deflagration of the salt- 

 petre is cfFccled. 



The prailical observation to be deduced from the above 

 experiment, is, that the soil or mould which contains the 

 most vegetable ojt carbonaceous matter will deflagrate 

 the greatest quantity of salt-petre; or, in other words, 

 that it will require less mould to deflagrate a given 

 weight of salt-petre, in proportion as that mould contains 

 a greater proportion of inflammable matter. 



The presence and proportion of vegetable and inflam- 

 mable matters in clay may, in some degree, be proved 

 and ascertained by the degree of blackness in the colour, 

 which the interior parts of the clay assume, when sub- 

 jeded in the fire to a certain degree of heat. 



The existence and proi)ortion of most saline matters in 

 soils are to be discovered by lixiviation, with warm water, 

 and by subsequent chrystallization. 



Gypsum is to be detefled by boiling the earth with al- 

 kaline salts ; in which case, the gypsum will be dccompos- 



cd, 



