ABSOLUTE WEIGHT AND FIRMNESS OF SOILS. 291 



Thu8^ cubic foot of dry 



Siliceous or Calcareous Sand — weighs about . 1 10 lbs. 



Half Sand and half Clay 95 



Of common arable Land, from . . . . 80 to 90 

 Of pure agricultural Clay (page 231) ... 75 

 Of garden Mould, richer in vegetable matter . 70 

 Of a peaty Soil, from 30 to 50 



Sandy soils, therefore, are the heaviest. The weight diminishes with 

 the increase of clay, and lessens still further as the quantity of vegetable 

 matter augments. 



In practice, the denser a soil is, the less injury ■w'ill be done to the 

 land by the passage of carts and the treading of cattle in the ordinary 

 operations of husbandry. In a theoretical point of view it is of conse- 

 quence to vegetation, chiefly in so far as, according to the experiments 

 of Schiibler, the denser soils retain their warmth for a longer period when 

 the sun goes down, or a cold wind comes on. Thus a peaty soil will 

 cool as much in an hour and a half as a pure clay in two, or a sand in 

 three hours. 



2°. Of the state of division of the constituent parts of the soil. — 

 With the relative weight of different soils, their state of division is in 

 some degree connected. Some soils consist of an admixture of exceed- 

 ingly fine particles both of sand and clay — while in others, coarse sand, 

 stones and gravels, largely predominate. There can be no doubt that the 

 state of the soil in this respect has a material influence upon its produc- 

 tive character, and consequently upon its money value, since the labours 

 of the husbandman in lands of a stiffer and more coherent nature are 

 chiefly expended in bringing them into this more favourable powdery con- 

 dition. In the description and examination of a soil, therefore, this pro- 

 perty ought by no means to be passed lightly over — since it is one in 

 regard to which a mere chemical analysis gives us little or no informa- 

 tion. 



In some parts of the country, the farmer diligently gathers th^. 

 stones off' his land, while in others the practice is condemned as hurtful 

 to the arable crops. The latter fact is explained by supposing that 

 these stones in winter afford shelter to the winter-corn, and in warmer 

 seasons protect the ground in some degree from the drying winds, and 

 retain beneath them a supply of moisture of which the neighbouring 

 roots can readily avail themselves. 



3°. Firmness and adhesive power of soils. — When soils dry in the 

 air they cohere and become hard and stiff"in a greater or less degree. 

 Pure siliceous sands, alone, do not at all cohere when dry — while pure 

 clays become hard and very difficult to pulverize. In proportion to the 

 quantity of sand with which the latter are mixed, do their tenacity and 

 hardness diminish. The diffici^ of reducing clays to a fine powder in 

 the open field, or of bringing them into a good tilth, may be overcome, 

 therefore, by an admixture of sand or gravel, but there are few localities 

 where the expense of such an operation does not present an insur- 

 mountable obstacle. Thorough draining, however, subsoil ploughing, 

 and careful tillage, will gradually bring the most refractory soils of this 

 character into a condition in which they can be more perfectly and more 

 economically worked. 



