68 A TREATISE ON THE CONNECTION OF 



rious, from its greater degree of insolubility : but gyp- 

 sum, far from being hurtful to vegetation when applied 

 to certain soils, promotes vegetation in a very high degree, 

 as is evinced by the use of it in some parts of the Conti- 

 nent of Europe and of America ; and is further proved by 

 the chemical analysis of vegetables, whose ashes are 

 found to contain a certain portion of the component parts 

 of gypsum. For the particular explanation of its mode 

 of ailing on soils suited to it — See Vitriolic Acid. 



SULPHAT OF MAGNESIA, OR EPSOM SALT. 



S'ULPHAT of magnesia, or Epsom salt, is not to be 

 found in such abundance as allum or gypsum : it is con- 

 tained in sea water, and is to be procured in greater quan- 

 tities by decomposing the muriat of magnesia, or the 

 bitter refuse liquor of salt works, by the means of the 

 vitriolic acid. Native Epsom salt is sometimes to be met 

 with in the mineral strata, mixed with clay and siliceous 

 matter. It is formed in soils containing alluminous 

 schyst, or pyrites, and a due proportion of the earth of 



a magne- 



