128 SCIENCE OF AGRICULTURE. 



ment, for the mutual action of the elements of sili- 

 cates, derived from their admitted electrical states, 

 yet the amount of this action is never measurable in 

 one season. Being silicates, they have no tendency 

 to act on each other. We can only excite this ac- 

 tion by introducing new elements, salts, which in 

 this sense only, can be said to be excitants or stimu- 

 lants. The silicates are the flour, the salts the 

 yeast. The galvanic agency is excited by the salts, 

 but above all, over all, and controlling all, this action 

 of soils is the living plant." — Dr. Samuel L. Dana. 



Manure. 



Manures are either substantive, that is, the food 

 of plants in a soluble state, or adjective, possessing 

 the power of rendering soluble the geine of the soil. 

 All animal substances, the droppings and urine of 

 cattle included, are, in part substantive, and in part 

 adjective manures. Undergoing decomposition, they 

 give out ammonia, an alkali in the form of gas, but 

 capable of uniting with water, and which, like pot- 

 ash and soda, is a solvent of geine. It is a compound 

 of one volume of azote, and three volumes of hydro- 

 gen. During the process, which converts fresh into 

 well rotted manure, ammonia escapes and is lost. If 

 the rotting manure be covered by soil, or what is 

 much better, peat muck, the ammonia unites with 

 the geine, and makes a valuable compost. Economy 

 requires that all barn manures, in their fresh state,, 

 should be mixed with such muck to form compost. 



Geine, or substantive manure, is the product of 

 putrefaction. The art of causing vegetable matter to 

 putrefy without running into the vinous or acetic fer- 

 mentation, either in compost heaps, or when plough- 

 ed into the soil, is a desideratum in agriculture. 

 Vegetable juices which contain sugar, starch, gum,, 

 and glutin, if exposed to air, moisture, and a temper- 

 ature never below 50° F., nor above 86° F., ferment 

 and are converted into gases, alcohol and yeast. 



