402 



SOI 



so f 



action of the atmosphere, is useful, 

 and putrid and calcareous manure 

 is necessar)- in the course of its 

 cultivation, Dr. Kirwan asserts 

 that •' the hest manure for clayey 

 soils is marl, or a mixture of marl 

 an i dung." See Clay and Clay 

 Soil. 



4. Peat. This substance is of 

 vegetable origin, chiefly compos- 

 ed of various sorts of aquatics, im- 

 mersed in stagnant water. In con- 

 verting peat into earth it is a rule 

 to plough and dig it in autumn, that 

 it may be exposed to the winter's 

 frost. See Peat. 



5. Chalk. Chalky soils, as before 

 observed, are seldom found in this 

 CO intry. A description of such 

 soils and their mode of cultiva- 

 tion may be found in The Code 

 of Agriculture, under the head 

 Soil. 



6. Alluvial Soils are of two sorts ; 

 one derived from the sediment of 

 fresh, and the other of salt water. 

 See Marsh and Meadow. 



7. Loam. Loams are said to be 

 the most valuable of all soils. They 

 are peculiarly well adapted to the 

 convertible husbandry, for they can 

 be altered not only without injury, 

 but generally with benefit from 

 grass to tillage, and from tillage to 

 grass. They should not, however, 

 be kept in tillage too long, nor 

 while they are in cultivation, should 

 two white crops be taken in suc- 

 cession. See Loam. 



Soils are of various colours ; {he 

 principal are white, black and red. 



White stiff clays are heated with 

 difficulty, and retain their heat on- 

 ly for a short time. 



A black soil, containing much 



vegetable matter, is most easily 

 heated, and soonest cooled. 



The red colour in eoils, is owing 

 to iron in various combinations. It 

 is favourable or adverse toferfility, 

 according to the natureof the com- 

 bination. 



There are various modes of im- 

 proving soils. 



" Soils with acids, or salts of 

 iron, may be amel4orated by the 

 application of earthy lime or chalk. 

 The sulphate of iron is thus con- 

 verted into a manure. If there be 

 an excess of calcareous matter in 

 the soil, it may be improved by the 

 application of sand, or clay, or 

 earthy substances. Soils too abun- 

 dant in sand, are benefited by the 

 use of clay, or marl, or vegetable 

 matter. A deficiency of vegetable 

 or animal matter must be supplied 

 by manure.- An excess of vegeta- 

 ble matter is to be removed by 

 burning, or to be remedied by the 

 application of earthy materials. 

 The substances necessary for im- 

 proving soils are seldom far distant. 

 Coarse sand is often found im- 

 mediately upon chalk, and perhaps 

 always under it, while beds of sand 

 and gravel are commonly below 

 clay, and clay and marl general- 

 ly below sand." Code of Agricul- 

 ture. 



The constituent parts of soils, 

 chemically considered, are certain 

 compounds of the earths, silica, 

 lime, alumina, magnesia, and of the 

 oxides of iron and magnesium ; and 

 animal and vegetable matters in a 

 decomposing state, and saline, acid 

 or alkaline combinations. For a 

 particular description of these, to- 

 gether with the mode of analysing 



