C. T. JxVCKSON'S ADDRESS. 459 



papers should be discarded, as leading to error, and as injurious 

 to society.* 



Organic Manures. — Although it is evident that the first veg- 

 etation of our globe grew withoiit the aid of organic manures, 

 or those derived from the decay of organic matter, either of 

 vegetable or animal origin, and we know that the lower classes 

 of plants, such as lichens, and mosses will grow without any 

 other nourishment than what they derive from rocks, water, 

 and the atmosphere ; still it is no less certain, that profitable 

 agriculture cannot be carried on without the aid of decompos- 

 ing vegetable and animal substances. 



Vegetable matters by decay produce acids, and these acids 

 decompose the minerals in the soil, and form neutral combina- 

 tions with the alkaline and earthy bases, rendering many of 

 them soluble in water. 



They also absorb and fix the ammonia, generated by the de- 

 cay of animal matters, and form valuable soluble compounds, 

 which are digestible by plants.f These acids may be called 

 the vegetable acids of the soil. 



The most common acids formed by the decay of vegetable 

 substances in humid soil are humic acid, apocrenic acid, ulmic 

 acid, and crenic acid, and a matter called extract of humus. 

 Besides these, there are neutral substances, called humin, ul- 

 mine, and coal of humus, which, by the action of the air, are 

 changed into other substances, and become soluble in water. 



These vegetable acids of the soil, form combinations with 

 the various alkaline and earthy matters, and are carried with 

 them into the circulation of living plants, in which the organic 

 substances are assimilated or converted into the sap of the plant, 

 and ultimately into the substance of its tissues. 



Animal matters, whether solid or liquid, by decomposition 

 always form alkaline matter, chiefly ammonia, and its salts. 

 This alkali corrects the acidity of the soil, combines with the 

 vegetable acids, extracts them from their insoluble compounds, 

 and renders them highly soluble in water. It decomposes nox- 



* The agricultural newspapers formerly abounded with " easy methods of analyzing the 

 soils," but happily we do not see them so often at this day. 



t This 1 liave proved by direct experiments with apoerenate of potash. 



