198 SCIENTIFIC AGRICULTURE. 



Oil calces, from cotton and linseed exhausted of their oils, 

 are valuable as fertilizers ; but their value for fattening animals 

 perhaps exceeds that as a manure, and may prevent their 

 direct use for this purpose. 



Peat, is used with benefit on soils which are deficient in 

 organic matters : it decomposes slowly, especially if sour or 

 applied alone to a wet soil containing little lime. Its action, 

 when properly decomposed and prepared, is the same as that 

 of other vegetable matters : it usually contains more or less 

 mineral and gaseous matters, which have their own peculiar 

 operation ; but these are not to be considered as affecting the 

 vegetable character of peat as a manure. On account of the 

 slowness with which it decays, it should be mixed with lime, 

 gypsum, wood ashes, or some vegetable matter which decom- 

 poses rapidly, such as farm-yard manure : swamp muck and 

 humus are similar in properties to peat. 



Tanners' bark, is used as a manure, but is liable to the 

 same objection as peat 'in respect to its slow decay: it is bes^ 

 brought into a state of fermentation by mixture with lime and 

 farm-yard manure in composts. 



Soot, is a complicated substance, as will be seen by refer- 

 ence to the table : it contains many things necessary to vegeta- 

 tion, and is a manure of some value ; but experiment has not 

 yet determined its precise character and operation. 



Charcoal, on account of its power of absorbing gases and 

 destroying offensive odors, is a valuable addition to the soil : 

 its operation is not so direct as that of some other manures; 

 that is, it is not so useful on account of any element which it 

 furnishes to plants, as by the intermediate office which it per- 

 forms of absorbing and retaining in the soil those volatile mat- 

 ters which plants require, and which would otherwise escape 

 and be lost. It is beneficial as a top dressing, and as an in- 

 gredient in composts : it evolves carbonic acid in its decompo- 

 sition, and is in this way directly useful to plants. Its power- 



