On Gypsum. 171 



tallizatioii, which escapes in combustion. Fitriolated 

 tartar^ glauber and epsom salts, and all combinations of 

 sulphuric acid promote vegetation. I believe, (though 

 I do not exactly know the fact) that gypsum contains 

 the greatest proportion of this acid, of any substance in 

 which it is combined, and its cheapness gives it a pre- 

 ference in husbandry. In it there are 48 parts of the 

 acid, and 34 of calcareous matter. It is not the only 

 salt beneficial to vegetation. Those not having this 

 acid in combination, produce useful effects. Salt pe- 

 tite fnitrat of potash) I have found highly beneficial, 

 when indian corn, before planting, was steeped in a so- 

 lution of this salt. All these salts are chymical com- 

 pounds; and require greater or less powerful solvents, 

 as well as gypsum; about which I stait no difficulties. 

 These solvents are furnished to them, in the laboratory 

 of nature as well as to the plaister. It is not well ascer- 

 tained that common salt fmuriat of sodg.) is a manure.* 



* It yet remains doubtful whether common salt is, or is not, 

 a manure, in its crude state. I have sometimes thought well 

 of it ; and used it in every way. When mixed with putres- 

 cent or putrefiable substances, judiciously, it is best. In 

 large quantities it prevents, though in small portions it pro- 

 motes putrefaction ; being antiseptic in one case, and septic 

 in the other. An incautious mixture of either salt (common) 

 or lime^ with the muck, or compost bed, often defeats the ob- 

 ject of their application. If lime be applied it consumes pu- 

 trescent substances, and forms insoluble compounds which 

 are inactive ; and they compose the greatest proportion of the 

 dung. Lord Dundonald decides against the use of salt, es- 

 pecially on poor land : he says that if it be at all useful, it is 

 On rich land. He highly recommends sea xvater for its great 



