274 



CULINARY OR KITCHEN GARDEN. 



and if it gained 165 grains, its specific gravity- 

 would be 1825, water being 1000. 



" The presence of clay and sand in any soil is 

 known— the first by its tenacity, the other by its 

 roughness to the touch, and by scratching glass 

 when rubbed upon it. 



"The presence of calcareous matter in soil 

 may be ascertained by simply pouring any acid 

 upon it, and observing if it effervesces freely. 

 Muriatic acid is the best for this purpose. Cal- 

 careous soils, magnesian soils and clays, are, for 

 the most part, softer to the touch than arenari- 

 ous soils. To ascertain the quantity of calcare- 

 ous earth present, dry soil thoroughly, and 

 weigh 100 grains of it, which gradually add to 

 1 drachm of muriatic acid, diluted with 2 

 drachms of water, in a phial poised in a balance ; 

 the loss of weight will indicate the escape of 

 carbonic acid, which will be 44 per cent of the 

 quantity of calcareous earth in the soil. 



" The presence of organised matter in any soil 

 may be ascertained very satisfactorily by weigh- 

 ing it after it is thoroughly dried, then subject- 

 ing it to a red heat, and weighing it again — the 

 weight so found will be the proportion of or- 

 ganic matter, and carbonic acid gas, if there 

 should be any. The same object may also be 

 attained by ascertaining the specific gravity of 

 the soil, but with less accuracy. 



" The presence of metallic oxides in a soil may 

 generally be known by their colour. Ferrugi- 

 nous soils are red or yellow ; cupreous soils 

 interspersed with greenish streaks, &c. Cupre- 

 ous impregnations of soils are rare, and the 

 usual green matter in such soils as the green- 

 sand of English geologists appears to be coloured 

 by iron, which is almost the only metallic im- 

 pregnation in considerable quantity in any soil. 



" The presence of salt, sulphur, coal, &c, may 

 be known by the absence or peculiarity of vege- 

 tation, as well as by colour, and the appearance 

 of the water of such soils. Saline soils may be 

 distinguished by the taste ; sulphureous soils by 

 their smell when thrown on a hot iron ; and the 

 presence of coal by its fragments, which will be 

 left after the soluble matters are removed by 

 water and muriatic acid. 



u The capacity of a soil for retaining water 

 may be thus ascertained : an equal portion of 

 two soils, perfectly dry, may be introduced into 

 two tall cylindrical glass vessels, in the middle of 

 each of which a glass tube has been previously 

 placed. The soils should be put into each in 

 the same manner, not compressed very hard, 

 but so as to receive a solidity approaching to 

 that which they possessed when first obtained 

 for trial. If, after this preparation, a quantity 

 of water be poured into the glass tubes, it will 

 subside, and the capillary attraction of the soils 

 will conduct it up the cylinders towards the top 

 of the vessels. That which conducts it most 

 rapidly, provided it does not rise from the 

 weight of the incumbent column of water in the 

 tube, may be pronounced to be the better soil.", 

 " Soils, considered scientifically," says Dr Mad- 

 den, " may be described to be essentially a mix- 

 ture of an impalpable powder, with a greater or 

 smaller quantity of visible particles, of all sizes 

 and shapes. Careful examination will prove to 



us that, although the visible particles have seve- 

 ral indirect effects of so great importance that 

 they are absolutely necessary to soil, still the 

 impalpable powder is the only portion which 

 directly exerts any influence upon vegetation. 

 This impalpable powder consists of two distinct 

 classes of substances ; viz., inorganic or mineral 

 matters, and animal and vegetable substances, in 

 all the various stages of decomposition. A very 

 simple method may be employed to separate 

 these two classes of particles from each other ; 

 viz., the impalpable powder and the visible par- 

 ticles ; and in so doing, we obtain a very useful 

 index to the real value of the soil. Indeed, all 

 soils, except stiff clays, can be discriminated in 

 this manner. The greater the proportion of the 

 impalpable matter, the greater, cceteris paribus, 

 will be the fertility of the soil. To effect this 

 separation, the following easy experiment may 

 be performed : Take a glass tube, 2 feet long, 

 closed at one end ; fill it about half full of water, 

 and shake into it a sufficient quantity of the soil 

 to be examined to fill the tube about 2 inches 

 from the bottom, then put in a cork, and, hav- 

 ing shaken the tube well to mix the earth and 

 water thoroughly, set the tube in an upright 

 position for the soil to settle down. Now, as 

 the largest particles are of course the heaviest, 

 they fall first, and form the undermost layer of 

 the deposit, and so on in regular gradation, the 

 impalpable powder being the last to subside, 

 and hence occupying the uppermost portion. 

 Then, by examining the relative thickness of the 

 various layers, and calculating their propor- 

 tions, a very accurate mechanical analysis of the 

 soil may be made." 



Colour of soils. — Soils vary in colour from 

 black to dirty white, the intermediate ones 

 being red, blue, brown, light yellowish brown, 

 &c. They derive these colours, for the most 

 part, from the oxides of iron contained in them, 

 and also from decomposing vegetable substances, 

 which all surface-soils contain in a greater or 

 less degree : some black soils may be totally 

 devoid of iron altogether, but these are few. 

 All very black soils, such as peat and deep 

 deposits of vegetable mould, are inert; and hence 

 so is old garden mould, long under cultivation 

 and gorged with organic manure. The protoxide 

 of iron is a powerful agent in communicating 

 a black colour, sometimes, in stiff clays. White 

 soils are chiefly over the chalk formation, and 

 the sandy deposits found near the sea-shore 

 are often of a yellowish white, both, however, 

 darkened by the addition of organic manure. 



Red soils, or rather dull brownish red, de- 

 rive their colour from peroxide of iron. 



Blue soils are found in the basins of stagnant 

 water, and in deposits of great depth, such as 

 the London basin of blue clay; they change 

 colour to a darkish brown by exposure and cul- 

 tivation. 



Brown and light-yellowish brown-coloured 

 soils are by far the most common as well as the 

 most valuable ; and although this colour is de- 

 rived from oxide of iron, it does not often exist 

 to a very injurious extent, excepting in gravelly 

 soils of a binding nature. A greater variety of 

 colour exists in subsoils ; and the brighter these 



