SOIL. 



other bodies that are united with tliem as primitive and con- 

 ftitiient parts of foils, in their original and native Hates ; 

 but having found that they all agreed in poflefling the pro- 

 perty of imbibing and retaining moifture, and thereby of 

 becoming foft and duftile, have, probably too haftily, con- 

 cluded them to have in fomemeafuie a fimilarity in their other 

 qualities. In this way erroneous notions have frequently, 

 he fuppufes, been engendered refpedling foils in which thefe 

 fubftances abound. For it is well afcertained, from the ufe 

 of clays in itates of greater purity, that there are eflential 

 differences in their qualities. There are fome forts, as that 

 which is denominated fuUer's-earlh, and feveral of the foft 

 boles that have the cohefive property in but a very flight de- 

 gree ; while others, (uch as thofe which are termed tills, are fo 

 extremely tenacious and vifcid, as to becapableof beingdrawn 

 out into threads : and there are ftill others, which, from their 

 foftnefs, and property of imbibing water readily, are capa- 

 ble of being cut with great facility by any (harp inftru- 

 ment ; while fome other forts are fo firm, hard, and compaft, 

 as fcarcely to admit of being foftened by means of water. 

 The clays which are employed for making the finell porce- 

 lain, and thofe ufed in the compofition of the more coarfe 

 wares, are only to be met with in particular fituations and 

 dillriits. This fully (hews that much diverfity muft exilt in 

 the nature of foils of this defcription, and which are per- 

 haps far from being yet fully iinderftood or afcertained. But, 

 befides foils of this fort differing in thefe refpefts, they have 

 an equal diverfity in their appearances or colours, and their 

 textures ; being found in the ftate of nature of very dif- 

 ferent colours, as red, white, blue, and yellow, and of very 

 different degrees of compaftnefs or denfity ; in fome cafes 

 readily admitting the intermixture of other matters to im- 

 prove them ; while in others they are highly refraftory in 

 •this refpeft, being with very great difficulty made to unite 

 with them. It is plain, therefore, that in the firlt of thefe 

 varieties of clayey foils, the proportion of filiceous or fandy 

 material mull be confiderably larger than in the latter, in re- 

 lation to that of the clayey part. But notwithftanding the 

 above, all thefe defcriptions of foils are found to polTefs 

 fome degree or other of the ftiff or heavy quality, accord- 

 ing to which, with proper attention to their other circum- 

 flances, their cultivation and improvement mull be conduft- 

 ed and carried on. 



The chemical analyfis of different forts of clays, executed 

 by the late ingenious Mr. Somerville, and detailed in his 

 valu-ible Survey of Ea(l Lothian, ferves to place the nature 

 of fuch foils in a clear point of view. 



The intelligent writer concludes, that the experiments 

 which he has defcribed feem to prove, that the principal 

 conftituent parts of fertile clays are alkaline falts, calcareous 

 earth, and oil, together with a very fmall proportion of 

 iron. In the ilronged and moil retentive clays, the pro- 

 portion of oil is greater, and that of alkaline fait and cal- 

 careous earth lefs, than in fuch as approach nearer to 

 the nature of loam ; except in the experiments, when the 

 clay was taken from the top of a lime-rock, in which it was 

 found to contain lefs oil than any of the others, and more 

 calcareous earth than either loam or any of the other clays : 

 it differs further in containing no iron. And it is fuppoled 

 that tills (j. e. a name given in Eaft Lothian to fuch of the 

 thin clays as are blue, yellow, and red coloured, and, at the 

 fame time, barren) contain the fame principles as other 

 clays, with the exception of calcareous earth, ef which they 

 appear to be entirely dettitute ; in place of which, they 

 contain a very great proportion of iron, which feems to be 

 the principal caufe of their barrennefs ; and, according as 

 they contain more or lefs cf it, they are more or lefs fterile. 



But in whatever manner thefe foils may be condituted, 

 they invariably require greater power, labour, and atten- > 

 tion, to bring them into a condition proper for the purpofes 

 of the farmer, than thofe of moll other forts. They are, 

 in fa£l, naturally llerile, from their adhering together in 

 maffes ; uiilefs where the fummer is fo divided between rain 

 and fun-(hine, that they are kept in a medium between 

 drought and wetnefs, a circumllance that rarely happens in 

 this uncertain climate. Where the feafons are wet, the 

 plants growing on fuch foils are inundated ; the clofenefs of 

 the clay not admitting the water to foak into the ground ; 

 and in a dry feafon the ground becomes fo folid, that the 

 roots of plants cannot penetrate or fpread themfelves in it. 

 A tolerably accurate idea of the fertility or barrennefs of 

 clayey foils may be obtained, by regarding the appearance 

 of the different plants, as they vegetate : if they appear 

 lively and vigorous, a favourable opinion may be drawn ; 

 the reverfe, of courfe, follows, if they appear languid, un- 

 healthy, and (tinted in their growth. 



However, the clayey foils are thought to contain more 

 of the food of plants than almoll any other ; as, -.vithout 

 much alteration, fuch lands will produce good crops of 

 grafs, provided care be taken not to feed them too clofely, 

 nor to admit cattle into them in the fpring. In order, how- 

 ever, to bring them into tillage, it is neceffary thai fuch 

 foils (hould be altered by the admixture of fuch fubllances 

 as tend to open the foil, and to break the cohefion of its 

 particles, and which fupply vegetable matter in many cafes. 

 When once thefe objefts are accomplifhed, the land will be- 

 come highly valuable, retaining manure excellently, and 

 never returning to its former ftate of barrennefs. Thefe 

 forts of foils are confequently capable of much improve- 

 ment, by the judicious application of fubllances and manures 

 of fuitable kinds, and a proper courfe of tillage hufbandry. 

 And in regard to the former, pounded limeltone, gravely 

 fand, and calcareous marie, are the moll ufeful articles in 

 the view of altering the texture ; and the bell feafon for 

 laying them on is in the beginning of the year, as it is only 

 during winter, while the furface is frozen, that teams can 

 ftir upon them. Where thofe fofTile fubftances cannot be 

 procured, and the vegetable principle is deficient, a mixture 

 of dung and fand, efpecially that from the fea-(hores, will 

 contribute greatly to fertihze the ground. But the appli- 

 cation of lime alone has, in many inltances, been attended 

 with great advantage ; though fome farmers difapprove of 

 it, on account of its being apt to cake, and not mixing in- 

 timately with the foil. However, a variety of other fub- 

 ftances may likewife be employed, in cafes where a deficiency 

 of thofe fofTils exift, fuch as comports of chalk and dung, 

 tanners' bark, fea-mud, and other materials that promote a 

 ftrong fermentation : and it has been found by experience, 

 that chalk and thefe together not only enrich the foil, but 

 alfo make it produce earlier crops than it did before. The 

 chalk, indeed, thus laid upon the land at length fubfides, 

 fettles as deep as the plough goes, and is then of no further 

 value in opening the land ; but it mav be recovered and 

 brought up again to the furface, by ploughing fomewhat 

 deeper than ordinary, after which it will produce its former 

 good effefts. Gravel from neighbouring foils may alfo be 

 carted upon clayey foils, to which may be added fea or pit- 

 coal afhes, duft from faw-pits, chips, and rubbilh from the 

 back yards of houfes, draw, and ftubble, rotten wood, 

 burnt clay, peat a(hes, and perhaps gypfum, or plalter of 

 Paris in fome cafes. This lall fubftance, as well as thofe 

 of lime and other calcareous matters, may alfo be found 

 ufeful in fuch foils of this fort as have a four tendency, by 

 neutralizing and correfting fuch acidity, by which they 



may 



