328 



PL A 



PL A 



and in the dung of cattle fed on 

 grass ; and it is not taken up in 

 corn crops, or crops of pease and 

 beans, and in very small quantities 

 in turnip crops ; but where lands 

 are exclusively devoted to pastur- 

 age or hay, it will be continually 

 consumed. Lord Dundas informs 

 me, that having tried gypsum with- 

 out any benefit on two of his es- 

 tates in Yorkshire, he was induced 

 to have the soil examined for gyp- 

 sum, and this substance was found 

 in both the soils." — Elements of 

 Agncidlural Chemistry, p. 224, 

 225. Philadelphia Edition. 



It has been made a question, 

 whether burning and calcining 

 gypsum make any difference with 

 regard to its fertilizing properties. 

 This is said to be the practice of 

 the French cultivators, and was 

 likewise recommended by Mr. 

 Deane. But an English writer on 

 agriculture says, that "calcining 

 is not likely to make any ditfer- 

 ence, because the sulphuric acid 

 in gypsum cannot be expelled by 

 the most violent heat of the fur- 

 nace ; and an experiment of Ar- 

 thur Young countenances the as- 

 sertion, that the effects of gypsum 

 are the same, whether calcined 

 or rough." Others have suppos- 

 ed that the sulphuric acid, which 

 forms one ingredient of gypsum, 

 " diluted with water by the che- 

 mistry of nature," may be instru- 

 mental in converting the starch of 

 plants into sugar. "As- starch 

 boiled in water with sulphuric 

 acid, and thereby changed into su- 

 gar, increases in weight without 

 uniting with any sulphuric acid or 

 gaS; or without forrai^ng any gas. 



we are under the necessity of as- 

 cribing the change solely to the 

 fixation of water. Hence we must 

 conclude that starch sugar is no- 

 thing else than a combination of 

 starch wi'th water in a solid state. 

 The sulphuric acid is neither de- 

 composed, nor united to the starch 

 as a constituent ; nevertheless it is 

 found that long boiling in pure wa- 

 ter does not convert the starch into 

 sugar.* This fact opens a large 

 field for rational speculation on the 

 physiology of vegetables ; as it 

 renders it possible that some of the 

 mineral acids in the sap of plants, 

 after acting chemically on the 

 juices concocted into pulp, may be 

 thrown out unchanged ; they may 

 alter the flavour without entering 

 into the essence. 



" Another step in the process of 

 conversion brings us to pure sul- 

 phur. Some plants yield this on 

 analysis. Seeds sown by way of 

 experiment on nothing but this 

 mineral, have produced healthy 

 plants ; and many soils, which na- 

 ture has impregnated with sulphur, 

 are highly fertile."! 



It is possible that the sulphuric 

 acid contained in gypsum may give 

 that substance its principal value 

 as a manure. And it would be 

 well to ascertain, by experiment 

 the efficacy of sulphuric, and other 

 mineral acids, by applying them, 

 in a very diluted state, as a liquid 

 manure to plants, and likewise to 



* See a Translation of the original Paper, 

 iu Annals of Philosophy, for December 

 1815. (No. XXXVI. pp. 425, 426.) 



t See a Treatise on Soils and Manures, 

 appended to the Philadelphia Edition of 

 Elements of Agricultural Chemistry, Article 

 Gi/psum. 



