ISO .»* MANURE 



tions necessary for their production be pre-ent at the same 

 time. 



All these conditi . i:s are united is liquid and solid excrements; 

 none of them are absent. In these are present, not only ammo- 

 nia, but also alkalies, phosphates, and sulphates, in the relative 

 pre rtion in which they exist in our cultivated plants. 



The p3\verful action -f urine depends, therefore, not only on 

 its compounds of nitr "»gcn ; for the phosphates and sulphates ac- 

 companying these take a decided part in the action. 



Urine, in the state in which it is used as manure, does not con- 

 tain urea, as this substance has been converted into carbonate of 

 ammonia during putrefaction. In dung reservoirs, well con- 

 structed and protected from evaporation, the carbonate of ammo- 

 nia is retained in solution. When the putrefied urine is spread 

 over the land, part of its carbonate of ammonia evaporates along 

 with the water, while another portion is absorbed by the soil, par- 

 ticularly if it be clayey and ferruginous land; but, in general, 

 only the phosphate and muriate of ammonia remain in the ground. 

 The amount of the latter alone enables the soil to exercise a 

 direct influence on the plants during the progress of their growth ; 

 and as they are not volatile, not a particle of them escapes being 

 absorbed by the roots. 



The existence of carbonate of ammonia in putrefied urine long 

 since suggested the manufacture of sal-ammoniac from this ma- 

 terial. When the latter salt possessed a high price, this manu- 

 facture was carried on by the farmer himself. For this purpose 

 the liquid obtained from dunghills was placed in vessels of iron 

 and subjected to distillation ; the product of this distillation was 

 then converted into muriate of ammonia by the ordinary methods 

 (Demachy). 



The carbonate of ammonia formed . y the putrefaction of urine 

 can be fixeJ, or be deprived of its volatility, in many ways. 

 When a field is strewed with gypsum, and then with putrefied 

 urine, or with the drainings of dunghills, all the carbonate of 

 ammonia is converted into the sulphate, which remains in the 

 soil. 



But there are still simpler means of effecting this purpose : 

 gypaum, chloride of calcium, sulphuric or muriatic acid, and 



