584 Transactions of the American Institute. 



GYPSUM, OR SULPHATE OF LIME. 

 C, 0. S0,+2 HO. (Sp. gr. is 2.322; percentage of water, about 2G.47.) 



When gypsum is broken into small pieces and calcined till it is 

 nearly anhydrous, and then ground to a powder, it is plaster of 

 Pans. When this is made into a paste with a little water, it sets, 

 and forms a hard coherent mass, which is called stucco; and has 

 the same composition as native gypsum. 



Sulphate of lime has nearly the same degree of solubility, at all 

 temperatures, and requires more than 460 parts of cold water for 

 solution. 



It has been extensively employed as a fertilizer, in various coun- 

 ti'ies, for a long time. In the Uuited States it is applied with 

 advantage to almost every crop. In many cases it is sown with 

 ^e seed; in others, it is put into the drills or holes, along with 

 tnanure, and frequently dusted over the young plants early in the 

 spring. The mode of applying it should depend upon climate and 

 quality rof soil. 



Gypsism requires, as has been already stated, 460 parts of wat^r 

 to dissolve it. Therefore, in dry climates, soils or seasons, it might 

 prove of little effect, if only dusted over the tops of the young 

 plants. 



Prof. Johnson, of the Royal Agi'icultural Society, while referring 

 to experiments of Prof. Korte, remarks that " it would appear that 

 time and mode of application has more influence on its effects than 

 might be supposed," and cites the following results and experi- 

 ments on clover, at different periods in the spring, from the same 

 field: 



Undressed 100 pounds. 



Top dressed, 30th March. 132 do 



Top dressed, 13th April 140 do 



Top dressed, 27th April 156 do 



The conclusion, therefore, was that the effects of the top dress- 

 ing was greatest when it is applied after the leaves have been 

 -well developed. 



An explanation of the action of the sulphates of lime, potash, soda 

 and magnesia may be deduced fi^om chemical analysis of the ashes 

 of plants and agricultural experiments. 



By the former, it is found that sulphur is a constant constituent 

 of gluten, albumen and other proteine compounds. Every one 

 .hundred pounds of these contain one-half to two pounds of sulphur, 



