AGRICULTURE WITH CHEMISTRY. 



107 



however, been analysed with more care, and when newly- 

 made, they probably would have been found to contain 

 a hepar of lime, a salt which is soluble in water ; whilst 

 gypsum, to which it reverts on exposure to air, is inso- 

 luble. To this hepar may the fertilizing power of these 

 ashes most probably be ascribed. 



As mineral springs are frequently found to arise in 

 peat mosses, it necessarily follows, that the ashes of dif- 

 ferent peat will contain very different saline and other 

 matters. When a too large proportion of vitriol of iron, 

 or green vitriol, is contained in peat, its ashes must of 

 course be inimical to vegetation ; but the injurious 

 effedls of this salt are to be correcfled by the addition of 

 lime, magnesia, alkaline salts, or dung. Of these sub- 

 stances, the preference is to be given to magnesia and 

 .alkaline salts ; for, whilst they decompose the metal- 

 lic salt, they form Epsom salt, Glauber salt, or vitrio- 

 lated tartar, all of which arc conducive to vegetation. 

 The cffeft of dung on such ashes requires to be explain- 

 ed in a different manner. The iron, in this case, is by the 

 ajiplication of the dung changed into a metallic state ; 

 whilst the vitriolic acid combines with the volatile alkali 



o 2 of 



