as a Manure. 87 



they do not contain the limestone principle, or at 

 least not in a sufficient degree, to answer the full pur- 

 poses of vegetation, Here the plaster acts power- 

 fully, whereas its influence cannot be discovered in 

 the dark calcareous soils, mixed with limestone. 



I have traced two rows of Indian-corn, half a mile, 

 which were plastered for an experiment, and never 

 could discover the least change produced by the plas- 

 ter in the soils near limestome-breaks (as we call 

 them), which were evidently highly calcareous. But 

 where the rows passed over thin, pale-coloured 

 land, particularly on knolls, at a distance from lime- 

 stone, the corn showed, that a great change had been 

 produced by the plaster ; not that it was better than 

 that growing upon the limestone spots, but that it 

 was equally luxuriant ; whereas without the aid of 

 plaster, it would not have been half as good. 



Frederick- County, May 28tb, 

 1804. 



The Editor will thankfully receive any additional 

 facts and observations, from any of his correspondents, 

 concerning the use of Gypsum, as a manure, in the 

 United- States. Even conjectures concerning the mode 

 of its operation, will be acceptable. 



