AGRICULTURE WITH CHEMISTRY. 



41 



SULPHUREOUS SCHYST. 



This substance generally accompanies the strata of 

 coal and limestone. For the most part it consists of clay 

 and pyrites, /. e. iron mineralised by sulphur, with a pro- 

 portion of calcareous matter and magnesia, the whole 

 tinged with a black, blue^ or grey colour, by mineral tar 

 or oil. By exposure to air vitriolic acid is formed ; this, by 

 combining with lime, magnesia, earth of iron, or clay, 

 forms gypsum, Epsom salt, green vitriol, or allum. 



Sulphureous schyst a6ts powerfully as a manure to 

 soils containing much phosphat of lime, or calcareous 

 matter. It is found, in the greatest abundance, in the 

 East part of the North Riding of Yorkshire, and is there 

 called allum rock. 



LIME. 



