266 



CULINARY OR KITCHEN GARDEN. 



with the earthy materials of the rock. In this 

 improved soil more perfect plants are capable of 

 subsisting ; these in their turn absorb nourish- 

 ment from water and the atmosphere, and, after 

 perishing, afford new materials to those already 

 provided. The decomposition of the rock still 

 continues; and at length, by such slow but gra- 

 dual processes, a soil is formed on which even 

 forest trees can fix their roots, and which is fitted 

 to reward the labours of the cultivator. Such, 

 therefore, being the opinions offered regarding 

 the primary formation of soils, let us briefly 

 consider them in the order in which they stand 

 above. 



Argillaceous or clayey soils derive their name 

 from, and are formed of substances, the basis of 

 which is argil or alum en, alumina or alumine, 

 the oxide of aluminum, one of the newly disco- 

 vered terrigenous metals, which unites with only 

 one proportion of oxygen, and forms the well- 

 known base called alumina, which contains, in 

 one hundred parts of " aluminum," about eight 

 of oxygen. Sir H. Davy laid it down as a rule in 

 practice, that the name clayey soil should not be 

 applied to any soil unless it contained one-sixth 

 of impalpable earthy matter, and did not effer- 

 vesce to any great extent with acids. Argilla- 

 ceous soils occur in extensive and often very 

 thick beds in most alluvial districts, transported 

 thither by the agency of water, and accumulating 

 for ages. This soil is much mixed with silica and 

 other matters, and is found of different colours, 

 as oxide of iron in different states and combina- 

 tion is amalgamated with it. Clay enters into 

 all good soils ; in fertile ones it abounds to the 

 extent of 9 to 15 per cent, whilst in barren lands 

 it exists to from 20 to 40 per cent. " The 

 absence of it," Donaldson observes, "forms a 

 soil too dry and porous : a proper quantity 

 forms the best clay lands and clayey loams, and 

 a superabundance of it constitutes a soil too wet 

 and cold for vegetable life, in a moist state, and 

 hardening and contracting by heat into a state 

 very hurtful to the growth of plants. The 

 purest clay contains upwards of 60 per cent of 

 sand, and is always mixed with mineral, animal, 

 and vegetable substances." Stiff or strong clays, 

 although they absorb the greatest quantity of 

 water when it is poured upon them, or in the 

 case of heavy rains, do not absorb most moisture 

 fiom the atmosphere in dry weather. They 

 then become caked on the surface, and evapo- 

 ration from below is consequently interrupted, 

 so that crops are burnt up on them sooner than 

 on light porous sandy soils. Clayey soils are 

 also much colder than lighter soils, because, from 

 their closeness of texture and often superabund- 

 ance of moisture, the rays of heat are prevented 

 from penetrating them. They are, however, 

 more uniform in temperature, as the same cause 

 that prevents the absorption of heat prevents 

 its radiation also. Clay has a strong affinity for 

 water, on account of the alumina forming its 

 basis retaining it with great tenacity; and it is this 

 quality which constitutes its distinguishing cha- 

 racteristic. " It may be remarked," says Donald- 

 son, " that this quality seems to exist in soils in 

 a smaller proportion than is generally supposed, 

 owing to the state of combination and exposure. 



Clay soils of all colours and qualities are known 

 by the property of holding water very tenacious- 

 ly; and when once wetted, they are dried with 

 very great difficulty. The most general colours 

 of clayey soils are red and black, of various de- 

 grees of fertility and texture. The red soils are 

 hardest; the black is softer, and in many cases 

 very waxy and plastic, arising from the minute- 

 ness of the particles affording so many points of 

 adhesion. In dry weather they are hard and 

 lumpy, as the red-coloured ; in moist weather 

 they dissolve more easily and readily. Clay soils 

 require much power and labour, and dry weather 

 if possible, during the process of being wrought, 

 and narrow ridging or thorough draining in 

 order to carry away the excess of moisture. Clay 

 soils, when well enriched with manures, are na- 

 turally well qualified for carrying good crops; 

 but they require much care and industry, as well 

 as a very considerable portion of practical skill 

 in their management, in order to keep them in 

 good condition ; yet, when the natural adhesive 

 toughness can be mastered, they generally yield 

 the heaviest and most abundant crops. One 

 grand requisite is, to keep the land in condition ; 

 a poor worn-out clay being the most ungrateful 

 of all soils, and hardly capable of repaying seed 

 and labour." Clay soils, although, when in a 

 high state of cultivation, capable of produc- 

 ing, during summer and autumn, most culinary 

 vegetables in a high state of perfection, are very 

 unfit for preserving them through the winter, or 

 for producing them early in the season. If 

 ameliorated by culture, and free from extra 

 moisture, they are well adapted for most of the 

 hardier sorts of fruit trees. The oldest speci- 

 mens of these with which we are acquainted are 

 growing in rich alluvial clayey soils. 



The composition of pure clay is thus given by 

 Donaldson, p. 15 : — 



Silica 0.35 



Alumina, .... 32.5 



Lime, ..... 0.35 

 Oxide of iron, .... 0.45 



Sulphuric acid, .... 19.35 



Water, .... 47.00 



100.00 



Silicious or sandy soils. — This term can only 

 with strict propriety be applied to soils having 

 at least seven-eighths of sand in their composi- 

 tion, and which do not effervesce when acids 

 are applied. Calcareous sandy soils, which may 

 be considered a variety of this soil, are readily 

 distinguished from the strictly silicious by effer- 

 vescing when acid tests are employed. " Sandy 

 soils are composed of the rough, dry, and hard 

 granulations of stones that have been disinte- 

 grated and reduced to particles by the action of 

 the various agencies that are supposed to have 

 contributed to the formation of the different 

 substances that are found in the composition of 

 the globe. Sands are much mixed with other 

 substances, and accordingly vary very much in 

 colour : white, red, yellow, brown, black, and 

 green, with many varieties, as the chief colour- 

 ing qualities are wanting or abundant. When 

 more unequally reduced, sand forms gravel ; 

 when composed mostly of flints, it is called 

 silicious ; with mica it is micaceous ; and when 



