C. T. JACKSON'S ADDRESS. 457 



vegetable and animals. It is found in soils generally combined 

 with silex, and is slowly eliminated by the decomposition of the 

 minerals containing it. 



Oxides of iron and manganese abound everywhere in all 

 soils, and we need not trouble ourselves to supply them by 

 composts or manures of any kind. They exist in all plants 

 and animals in small proportions. 



Sulphuric acid exists in soils in combination with lime, mag- 

 nesia, alumina, oxide of iron, and the alkalies, and goes into 

 the circulation of plants, generally in combination with lime, 

 ammonia, and the fixed alkalies. It is not only separated 

 in part from its mineral combinations during its circulation in 

 plants, but is actually reduced in some of them, sulphur being 

 known to exist in a free state in most of the cruciferous plants, 

 such as the mustard, turnip, cabbage and cauliflower. Every 

 housewife is familiar with the action of mustard on a silver 

 spoon, the blackening being due to the action of sulphur, which 

 combines with the silver. 



Sulphate of lime or gypsum, is supposed to owe part of its 

 fertilizing power to its exchange of elements with carbonate of 

 ammonia arising from the decomposition of animal manures, 

 sulphate of ammonia and carbonate of lime resulting; but it is 

 certain that clover and some other plants also appropriate sul- 

 phate of lime in its undecomposed state. Sulphate of ammo- 

 nia is the most powerful of the soluble sulphates, for it conveys 

 nitrogen and hydrogen to the plant as well as sulphuric acid. 

 It is not known exactly how this saline manure acts, but it has 

 been proved, by experiment, to be one of the most powerful, 

 acting favorably when used in the minute proportions conveyed 

 by a steep for seed : this being the German secret of raising 

 grain from prepared seed without manure, a secret which made 

 so much noise in the agricultural world a few years since. 



Chlorine, in combination with the metallic bases of the al- 

 kalies, and with those of magnesia and lime, enters into the 

 composition of all plants, and is always found in such combi- 

 nations in their ashes. In some places, sea salt operates favor- 

 ably as a saline manure, and increases generally the crops of 

 grass. It is also favorable to the plum tree, and to vegetables 

 58 



