NUTRITIVE MANURES, ^65 



which decompose slowly, and can retain water for a long 

 time, to furnish it to the wants of plants in seasons of 

 drought. 



It is by separating these principles, that we may be able 

 to appropriate the various kinds of manure to each species 

 of soil and plant : the attention of agriculturists is already 

 directed, upon this point, to the composition of mixtures 

 of manures, called composts. These are formed by ar- 

 ranging, one above another, beds of different kinds of 

 manure, taking care to correct the faults of one by the 

 properties of another, in such a manner as to produce a 

 mixture suited to the soil to be enriched by it. 



For example, if it be required to form a compost for a 

 clayey and compact soil ; the first bed must be made of 

 plaster, gravel, or mortar rubbish ; the second, of the lit- 

 ter and excrements of horses, or sheep ; the third, of the 

 sweepings of yards, paths, and barns, of lean marl, dry 

 and calcareous ; of mud deposited by rivers, of the fecal 

 matter collected upon the farm, the remains of hay, straw, 

 etc., and this in its turn must be covered with a laying of 

 the same materials as the first. Fermentation will take 

 place first in the beds of dung, and the liquor flowing from 

 these will mingle with the materials of the other layers; 

 when the mass exhibits the signs which I have pointed 

 out, as indicating decomposition to be sufficiently ad- 

 vanced, it must be carried into the fields, care being first 

 taken to mix well the substances composing the different 

 layers. 



If the compost be designed to manure a light, porous, 

 and calcareous soil, it must be formed of materials of a 

 very different character. In this case it is necessary that 

 argillaceous principles should prevail ; the substances must 

 be compact, the dung of the least heating kind, and the 

 fermentation continued, till the materials form a yielding 

 and glutinous paste ; the earths must be clayey, half baked, 

 and pounded, or consisting of fat and argillaceous marl, 

 and mud from the sea coast. Of these all the layers must 

 be formed. 



By following these principles in my operations, I have 

 completely changed the nature of an ungrateful soil in the 

 neighbourhood of one of my manufactories. Over this soil, 

 composed of calcareous earth and light sand, I spread, 

 during several years, some calcined clayey earth; and this 

 land, upon which I could formerly raise only stone fruit, 

 6* 



