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On Gypsum. 



Read April, 1815. 



Warren, (Va.) 26th March 1817. 

 Sir 



The third volume of the Memoirs of the Philadel- 

 phia Agricultural Society, contains some remarks on the 

 unsatisfactory manner, in which SirHumphery Davy has 

 treated of gypsum, ; as a manure, which have induced 

 me to submit to you the following hints on that sub- 

 ject. And, indeed, instead of shedding new light on 

 the matter, as we might have expected, he has expressed 

 doubts respecting some of its operations, which are fami- 

 liar to every observant farmer that has used it. Such, par- 

 ticularly, as its power of promoting putrescence when ap- 

 plied to vegetable substances, either on grass, or the damp 

 straw of a farm yard, or even on dry straw mixed with it, 

 and stacked for the purpose of experiment, seem to be ex- 

 cluded by the result of his experiment on minced veal. 

 Under all which circumstances, I know that gypsum has- 

 tens very much the dissolution of the substances submitted 

 to its action, but if I could not produce better authority 

 than my own, for dissenting from the opinion of a chemist 

 so eminent, I should not now trouble you with my own re- 

 specting it. 



Mr. Kirwan, in his treatise on manures, considers car- 

 bonic acid gas, as the most active principle of manure in 

 promoting the growth of plants; and Sir H. Davy concurs 

 with him, in his lectures on Agricultural chemistry ; if that 

 opinion be correct, we have the authority of Fourcrov fo>' 



