122 A PRACTICAL TREATISE 



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would become a real advantage. 2. That this stimulative 

 property is common to every substance that merits the name 

 of manure. That, although gypsum may not be possessed of 

 any nutritive quality in itselti yet, if the land be properly 

 dunged, or otherwise supplied with a sufficiency of other pu- 

 trescent manure, or of nutritive compost, to support the 

 increased powers of vegetation, — and which, in common pru- 

 dence, should never be neglected, — the soil will not, if dis- 

 creetly managed, suffer any diminution of its accustomed fer- 

 tility, but will be improved by the large addition made, 

 through the greater luxuriance of the green crops, to the size 

 of the dunghill. 3. That its beneficial effects being confined 

 to some peculiar species of crops, is no real disadvantage; for, 

 when applied to those of a different kind, it has not, in any 

 known instance, been found prejudicial. Its powers appear, 

 indeed, to apply more to tiie specific crop on which it is spread, 

 than to the state of the soil ; and when it has been laid in vari- 

 ous quantities — from two bushels to two-and-thirty^on crops 

 to which it is inappropriate, it has been found in all cases 

 wholly ineftectual. 



It has been assigned by Sir Humphry Davy, in the theory 

 by which the operation of gypsum is governed, as a general 

 standard for its application, that it is the most beneficial to 

 those plants which always aftbrd it on analysis : thus, the ashes 

 of lucerne, sainfoin, rye-grass, and clover, contain considera- 

 ble proportions of gypsum ; but only a very minute quantity is 

 to be found in crops of corn, pulse, or turnips. It is, therefore, 

 essential to the vegetation of the former ; and land which has. 

 grown tired of clover, may be restored by being dressed with 

 it, or with peat ashes, some species of which hold a large por- 

 tion of gypsum. But when the soil already contains a suffi- 

 cient quantity of this substance for the support of the cultiva- 

 ted grasses, he considers that its application to tliem, or even 

 to the natural pasture, cannot be advantageous; for plants only 

 require a certain portion of manure, and an excess may be 

 detrimental. The reason why its application to soils is not 

 always efficacious is, probably because it is furnished by the com- 

 mon course of culture to most well-cultivated land in sufficient 

 quantities for the use of the grasses, and perhaps to an excess 

 beyond what other crops require for their growth ; for although 

 this may not be apparent to the farmer, it is contained in sta- 

 ble dung, and in the dung of all cattle fed on pasture. A 



