SOIL. 



duAivenefs, ought, as has been feen, to be much greater in 

 warm and dry countries, than in cold and moilt ones ; and 

 the quantity of fine aluminous earth they contain larger. 

 Soils, likewife, as already feen, that are fituated on dechvities, 

 ought to be more abforbent than thofe in the fame climate, 

 on plains or in vallies. The produftivenefs of foils mud !ike- 

 wife be influenced by the nature of the fub-foil, or the earthy 

 or ilony ilrata on which they reft ; and this circumftance 

 ought to be particularly attended to in confidering their 

 chemical nature, and the fyflem of improvement. Thus, a 

 fandy foil may fometiraes owe its fertility to the power of 

 the fub-foil to retain water ; and an abforbent clayey foil 

 nay occafionally be prevented from being barren, in a moift 

 climate, by the influence of a fub-ftratum of fand or gravel. 

 In regard to the chemical compofition of fertile corn- 

 foils in this climate, thofe foils that are moft produftive of 

 corn, contain always certain proportions of aluminous and 

 calcareous earth, in a finely divided Itate, and a certain quan- 

 tity of vegetable or animal matter. The quantity of cal- 

 careous earth is however very various, and in fome cafes ex- 

 ceedingly fmall. A very fertile corn-foil from Ormifton, in 

 Eaft Lothian, afforded the writer, in an hundred parts, only 

 eleven parts of mild calcareous earth ; it contained twenty- 

 live parts of fihceous fand ; the finely divided clay amounted 

 to forty-five parts. It lolt nine in decompofed animal and 

 vegetable matter, and four in water ; and afforded indica- 

 tions of a fmall quantity of phofphate of lime. This foil 

 was of a very fine texture, and contained very few Itones or 

 vegetable fibres. It is not unhkely that its fertility was in 

 fome meafure connefted with the phofphate ; for this fub- 

 ftance is found in wheat, oats, and barley, and may be a part 

 of their food. A foil from the low lands of Somerfetfhire, 

 celebrated for producing excellent crops of wheat and beans 

 without manure, he found to confill of one-ninth of fand, 

 chiefly fihceous, and eight-ninths of calcareous marie tinged 

 with iron, and containing about five parts in the hundred of 

 vegetable matter. He could not deteft in it any phofphate 

 or fulphate of lime, fo that its fertility mull have depended 

 principally upon its power of attrafting principles of ve- 

 getable nourifhment from water and the atmofphere. And 

 Mr. Tillet found that a foil compofed of three-eighths of 

 clay, two-eighths of river-fand, and three-eighths of the 

 parings of limeftone, was very proper for wheat. 



With refpeft to the compofition of foils proper for bul- 

 bous roots and for trees, it is obferved that, in general, 

 bulbous roots require a foil much more fandy, and lefs ab- 

 forbent, than the grafTes. A very good potatoc foil, from 

 Varfcl, in Cornwall, afforded him feven-eighths of filiceous 

 fand ; and its abforbent power was fo fmall, that one hun- 

 dred parts loft only two by drying at 400° Fahrenheit. 

 Plants and trees, the roots of which are fibrous and hard, 

 and capable of penetrating deep into the earth, will vegetate 

 to advantage in almoft all common foils which are mode- 

 rately dry, and which do not contain a very great cxcefs of 

 vegetable matter. He found the foil taken from a field at 

 Sheffield- Place, in Suffex, remarkable for producing flou- 

 rifhing oat^, to confift of fix parts of fand, and one part of 

 clay and finely divided matter. And one hundred parts of 

 the entire foil fubmitted to analyfis, produced 



Subiiances, 



Water 



Silcx . - - 



Alumine 



Carbonate of lime 

 Oxyd of iron - 

 Decompofing vegetable matter 

 Lofs - - . 



Vol. XXXIII. 



3 

 54 

 28 



3 

 5 



4 

 3 



And on the advantages of improvements made by chang- 

 ing the compofition of the earthy parts of foils, it is ob- 

 ferved that, from the great difference of the caufes that in- 

 fluence the produftivenefs of lands, it is obvious that, in the 

 prefent ftatc of fcience, no certain fyftem can be devifed for 

 their improvement, independent of experiment : but there 

 are few cafes in which the labour of analytic trials will not 

 be amply repaid by the certainty with which they denote the 

 belt methods of amehoration ; and this will particularly 

 happen, when the defcft of compofition is found in the pro- 

 portions of the primitive earths. In fupplying animal or 

 vegetable manure, a temporary food only is provided for 

 plants, which is in all cafes exhaufted by means of a certain 

 number of crops ; but when a foil is rendered of the beft 

 pofTible conflitution and texture, with regard to its earthy 

 parts, its fertility may be confidered as permanently efta- 

 bhfhed. It becomes capable of attrafting a very large pro- 

 portion of vegetable nourifhment from the atmofphere, and 

 of producing its crops with comparatively little labour and 

 expence. 



There are different other cafes in which improvements 

 may be direfted in this way ; as where the falts of iron or 

 fome acid material is found to prevail in foils, they may be 

 altered and correfted by the ufe of lime in its moft aftive 

 ftate. In this manner very fterile foils, not deficient in tex- 

 ture, have been effeftually improved. When the quantity 

 of calcareous matter is too great, fand or clay is the obvious 

 remedy. If there be a deficiency of vegetable materials in 

 light fandy or gravelly foils, they may be permanently im- 

 proved by the ufe of peat earth upon them. The peat- 

 boggy and marfhy forts of foils, after proper draining, are 

 mollly made produftive, by laying upon them fandy, or 

 fliff earthy matters in due proportion, efpecially when the 

 former are of the black foft peaty quality. In cafes where 

 peaty foils are acid, or much impregnated with ferruginous 

 faline matters, the ufe of calcareous fubftances is eflentially 

 neceflary for bringing them into proper order. 



It is conceived that the beft natural foils are thofe, the 

 materials of which have been produced from ftrata of dif- 

 ferent kinds, which have been the moft perfcftly divided in 

 their parts by the operation of air and water, and are the 

 moft intimately blended and incorporated together. In im- 

 proving foils artificially, it is in fhort fuppofed, that the 

 farmer cannot do better than imitate the procefles of nature. 

 The materials fuitablefor the purpofe are, it is faid, feldom 

 far diftant : coarfe fand is often found immediately upon 

 chalk ; and beds of fand and gravel are commonly below 

 clay. 



The labour of amending and improving the texture and 

 conflitution of foils, is repaid, it is faid, by many great 

 permanent benefits ; a fmaller quantity of manure is re- 

 quired, and their fertility rendered fecure, &c. 



In order to afcertain the properties and qualitiei of land, 

 the method of chemical analyfis lias been adopted. In this 

 cafe the following rules and dircftions, laid down by pro- 

 fedbr Davy in the p.iper befor alluded to, may be found ufe- 

 ful in guiding the inquirer. All the varieties of foils may- 

 be analyfed in this way. 



I . Jnjlnimcnls required for the Analyjis of Soils — The really 

 important inftruments required for the analyfis of foils are, 

 in his opinion, few, and but little expcnfive. They arc, a 

 balance capable of containing a quarter of a pound of com- 

 mon foil, and capable of turning, when loaded, with a 

 grain ; a feries or let of weights, from a quarter of a pound 

 troy to a grain ; a wire ficve, fufhciently coarfe to admit a 

 pepper-corn through its apertures ; an Argand lamp and 



L 1 ftud; 



