ttYP9UM, OR ?LASr£R OF PARIS. 227 



Gypsum, or Plaster of Paris. 



It will be seen from various experiments, relative to the ap- 

 plication of plaster as a manure, that very different views have 

 been had respecting the best mode of rendering it most effica- 

 cious. Sir Humphrey Davy observes, that the reason why 

 gypsum is not generally efficacious, is probably because that 

 most cultivated soils contain it in sufficient quantities for the 

 use of the grasses. That in the common course of cultivation 

 gypsum is furnished in the manure ; for it is contained in sta- 

 ble dung, and in the dung of cattle fed on grass ; and it is not 

 taken up in corn crops, or crops of peas and beans, and in very 

 small quanties in turnip crops ; but when lands are exclusive- 

 ly devoted to pasturage or hay, it will be continually consumed. 

 He further observes, that Lord Dundas informed him, that 

 Kaving tried gypsum without any benefit, on two of his estates 

 in Yorkshire, he was induced to have the soil examined for 

 gypsum, and this substance, was found in both the soils.^ 



Col. Taylor, in answer to some questions by Mr. Jeffreys, 

 respecting the nature and effects of gypsum, observes, that he 

 sows from three pecks to one bushel of piaster upon an acre; 

 that It succeeded upon all soils to v^'hich he had applied it ; those 

 requiring to be drained excepted. Sown on clover in the 

 spring, it benefits it considerably ; that used in any oHier mode, 

 he ploughed it in. But I have, says he, even discontinued the 

 first practice, from observing that when plaster is sown and 

 ploughed in with wheat in the fail, a top dressing to the sub- 

 sequent clover is of little or no use ; and from thinking that the 

 effect of the plaster sooner ceases, as a top dressing, than 

 when ploughed in. That the best ways of using it are in the 

 spring, upon the long manure of the preceding winter, to be 

 ploughed in with it upon well covered fields, to be sown imme- 

 diately before they are fallowed. In rolling it very wet, vrith 



^ZUc Elements of Ajricaltural Chemistry^ p. 224, 225. Phil.ed. 



