FERTILIZERS. 67 



weather, are harder to reduce than fresh bones containing gelatine. As a general thing, it 

 will be found more satisfactory to purchase ground bone from the manufacturers, who have 

 every facility for putting them in a condition favorable and convenient for use. The only 

 objection is, that this material is often adulterated by mixing something of inferior value with 

 it, and the fraud is difficult of detection except by chemical analysis, which will neither be 

 convenient nor economical for the farmer to have done. The best safeguard will be to deal 

 only with manufacturers who have a good reputation for honesty in producing a pure article. 

 Mineral phosphates, as well as bones, furnish a supply of phosphoric acid to the agricul 

 tural world. They are found in South Carolina in great abundance, and are sometimes called 

 phosphate marls. They are supposed by geologists to be coprolites, or the excrementitious 

 remains of fossil animals, that seem to have congregated in great numbers in this region. 

 They are reduced with sulphuric acid, and are considered among the best of fertilizers. 



Gypsum, Plaster, or Sulphate of Lime. The pure gypsum, when ground and 

 subjected to the proper degree of heat, constitutes what is called &quot; Plaster of Paris,&quot; which is 

 so extensively used for stucco, hard-finish, and for various purposes in ornamental art. 



The most celebrated gypsum- beds are those of Montmartre, near Paris. In this country 

 gypsum is found in Nova Scotia, New York, Virginia, Tennessee, Michigan, and various 

 other localities. It is valuable as a fertilizer, containing lime, combined with sulphuric acid, 

 and a few other substances. 



The pure gypsum is usually white, but the ground land-plaster is white or light gray, 

 and sometimes of a dark gray, like that quarried in central New York. Its agricultural 

 value depends upon its amount of sulphate of lime principally, and cannot be judged of 

 accurately by its color or appearance after being ground. 



The use of gypsum is attended with great benefit to certain soils and crops, being best 

 adapted to sandy, loamy, or clay soils, though requiring a larger application to such soils as 

 contain a considerable amount of vegetable matter. Its use is especially beneficial to the pro 

 duction of the red and white clovers, grass, lucern, sainfoin, peas, beans, etc. It has been 

 found, by the experience of most farmers, that in the use of plaster, as with wood-ashes and 

 some other fertilizers, that the season has much to do with the benefits derived from its appli 

 cation; that gypsum requires a large amount of water, and when the season is very dry, the 

 benefits resulting, even upon the same field, are greatly inferior to those of a moist season; 

 also, another noticeable fact in its use is, that it almost always shows better results upon the 

 north and northeastern slopes of hills, than upon the southern. This can be accounted for 

 only in the fact that the northern slopes of hills are longer in the shade than the southern, 

 and usually have a heavier deposit of dew ; hence the soil there would contain more moisture 

 than the southern slopes, proving the necessity of a sufficient supply of moisture in attaining 

 the best results. 



Plaster is a great absorbent, and its efficiency is supposed to be in a measure attributable 

 to its power of absorbing and retaining ammonia, and furnishing it to plants to which it is 

 applied, as they have need. It is a very good absorbent to apply to the manure-heap, com 

 post-pile, and privy vaults, not only acting as a disinfectant, but, by thus mixing it with 

 ammonical manures, a sulphate of ammonia is obtained which is less volatile than carbonate 

 of ammonia, the natural product of these substances. 



When applied to the soil, the sulphate of ammonia more readily parts with its fertilizing 

 properties than the carbonate form, which effect is of course modified by the amount of 

 moisture in the soil. 



Liebig says on this subject: &quot;Soluble sulphate of ammonia and carbonate of lime are 

 formed, and this salt of ammonia, possessing no volatility, is consequently retained in the soil. 

 All the gypsum gradually disappears, but its action upon the carbonate of ammonia continues 

 as long as a trace of it exists.&quot; 



