MANURE. 195 



Let it be stirred occasionally for a week, and it will be fit for 

 use. Apply \l as spent lye, grounds and all. Both ashes 

 and salts may be doubled and trebled, with advantage, if 

 convenient. The mixture of lye must be used before it 

 begins to putrefy ; this occurs in three or four weeks. It 

 then evolves sulphuretted hydrogen gas, or the smell of gas 

 of rotten eggs. This arises from the decomposition of the 

 sulphates in the water and ashes, by the vegetable matter. 

 A portion of the geine is thus deposited from the solution. 

 (See Appendix for the trial of this lye.) 



239. Having thus considered the class of mixed manures, 

 or those composed of geine and salts, those consisting of 

 salts only are to be now explained. They are next in value 

 to the mixed manures. They are chiefly the liquid evacua- 

 tions of animals, and when artificially combined with geine, 

 their value exceeds that of the solid evacuations. These 

 liquids equal, in fact, the mixed manures of the most fertiliz- 

 ing energy. The liquid evacuations are truly salts only, dis- 

 solved in water ; but they are salts of a peculiar character 

 in many cases, and are formed of an animal acid. This is 

 it which renders a detailed account of these manures inter- 

 esting to the farmer. It is not enough for this purpose to 

 refer the action of these liquids to the general effect of salts 

 or mineral manures. 



240. The peculiar animal acid to which reference has been 

 made, becomes, like nitric acid in nitrates, the food of plants. 

 The element from which it is derived gives a marked and 

 highly valuable character to the liquid evacuations of the 

 farm-yard and household. This peculiar animal principle is 

 urea. It may be obtained from these liquids in transparent 

 but colorless crystals, of a faint but peculiar odor. Cold 

 water dissolves more than its weight, and boiling water an 

 indefinite quantity of crystals of urea. The pure crystals 



