SOIL. 



means of acids, may alfo, it is conceived, in fome meafiire, 

 depend on the attraftion of its different component particles 

 to each other. It is a fort of limeftone, which is found to 

 extend itfelf over very large diflridts in the midland parts 

 of the ifland, as well as in the more northern counties, as 

 is obvious from the praftical diftindtions of mild and hot Lmes, 

 which are in common ufe, as noticed by doftor Fenwick, 

 in his excellent Eifay on Calcareous Manures. 



It has indeed been fuggefted, that thefe interefting fafts 

 not only (hew, that whatever famenefs there may be m the 

 nature of calcareous matter, when in its pure and unadul- 

 terated ftate, but that, as met with in foils, and different fub- 

 ftances of the calcareous kinds, it has confiderable diverfity, 

 and when in union with magnefia, it is in a high degree pre- 

 judicial to the growth of vegetables. Later trials have, 

 however, rendered this laft fuppofition fomewhat doubtful ; 

 therefore, until further experiments have more completely 

 cleared up the matter, the farmer Ihould proceed with cau- 

 tion in the ufe of fuch materials. But though magnefian 

 lime or earth in its cauftic ftate may be injurious to vegeta- 

 tion, fuch lime, in ordinary circumlfances, is not unfre- 

 quently made ufe of in moderate quantities upon foils of 

 the fertile kind, in the counties of Leicefter, Derby, and 

 York, with good efteft, and is capable of being employed 

 in larger portions on foils containing more full fupplies of 

 vegetable matter. Magnefia, when combined with carbonic 

 acid gas, feems not, it is faid, to be hurtful to the growth 

 of plants, and in foils rich in manure, it is foon fupplied 

 with this principle, from the decompofition of that fub- 

 ffance. 



In explanation of the above, fir H. Davy has ftated, that 

 magnefia has a much weaker attraftion for carbonic acid 

 than lime, and will remain in the ftate of cauftic or calcined 

 magnefia for many months, though expofed to the air ; and 

 that as long as any cauftic lime remains, the magnefia can- 

 not be combined with carbonic acid, for lime inftantly at- 

 trafts carbonic acid from it. When a magnefian limeftone 

 is burnt, the magnefia is deprived of carbonic acid much 

 fooner than the lime ; and if there be not much vegetable 

 or animal matter in the foil to fupply by its decompofition 

 carbonic acid, the magnefia will remain for a long while in 

 the cauftic ftate ; and in fuch, afts as a poifon to certain 

 yegetables. And «hat more magnefian lime may be ufed 

 upon rich foils, than thofe of other kinds, feems to be 

 owing to the circumftance, that the decompofition of the 

 manure in them fupplies carbonic acid. And magnefia, 

 when mild or fully combined with carbonic acid, feems to 

 be conftantly an ufeful conftituent part of foils. Carbonate 

 of magnefia, produced by boiling the folution of magnefia 

 in fupercarbonate of potafla, has been thrown over grafs, 

 and upon growing wheat and barley, fo as to render the 

 furface white, without injuring the vegetation in the fmalleit 

 degree, by the fame experimenter. Some moft fertile dif- 

 trifts are alfo faid to contain mild magnefian earth, as the 

 Lizard, in Cornwall. 



This explanation has been fomewhat confirmed by mix- 

 ing and ufing four portions of the fame fort of foil in this 

 manner : with one-twentieth of its weight of cauftic mag- 

 nefia, with another the fame quantity of magnefia and a pro- 

 portion of fat decompofing peat, one-fourth of the weight 

 of the foil ; one portion was left in its natural ftate, and 

 one mixed with peat without magnefia. They were made 

 towards the end of the year, and fown in the early fpring 

 the next, all of thenrwith barley ; which grew very well, it 

 is faid, in the pure foil ; but better in the foil containing the 

 peat and magnefia ; and nearly a$ well in the foil with the 



peat alone ; but in the loil mixed with magnefia alone, »t 

 rofe very feebly, and looked yellow and fickly. The repe- 

 tition of this trial was attended with fimilar refults ; and it 

 was found, that the magnefia in the foil mixed with peal 

 became ftrongly eftervcfcent, while the portion in the an- 

 mixed foil gave carbonic acid in much fmaller quantities. 

 In the one cafe, it is fuppofed, the magnefia had allifted in 

 the formation of manure, and had become mild ; in the 

 other cafe it had afted as a poifon on the plants. 



It has alfo been found, that matter of the calcareous kind, 

 whether effete or in the ilate of carbonate, or in the more 

 aftive one of caufticity, as quickhme, feems ultimately to 

 promote the refolution and deftruAion of all vegetable and 

 animal fubftances ; but that in the latter ftate, it afts with 

 much greater violence on thefe materials, dellroying tl}eir 

 organization, and diflipating their principles more quickly, 

 as well as robbing them more completely of the carbonic 

 acid gas or fixed air, which is fo efiential ; while in the 

 former it operates with great mildnefs, and only aids the 

 refolution of thofe fubftances, by gently promoting the 

 procefs of putrcfaftion or decay. 



It muft be obviou";, that in them the proportions of 

 clayey, loamy, and gravelly ingredients, in combination 

 with the calcareous matters of thefe foils, are materially dif- 

 ferent m different diflrifts : where the clayey and loamy are 

 comparatively in large quantities, the heavier kinds of 

 chalky foils are met with ; but where the fandy or 

 gravelly are prevalent, the lighter ones. Material differ- 

 ences alfo arife from the earthy matter with which the cal- 

 careous fubitance is blended in the ftate of foil, as where 

 the quantity of this is fmall, and not reduced into any per- 

 feft ftate of mould, the foil is poor and thin ; but where 

 the thicknefs of this fuperficial bed or layer is confider- 

 able, and the animal, vegetable, or other fubftances of 

 which it is conftitutcd, have proceeded to a more complete 

 ftage of decompofition, the foils are more rich and heavy. 

 Where the ftate of the fub-foil is of a compaft nature, and 

 much blended with filiceous or flinty matter, or hat a mor- 

 tary hardnefs, it is lefs favourable than where it is of a more 

 open, brittle, or mellow powdery nature. From the cal- 

 careous material being abundant in thefe cafes, the principal 

 intention is the changing of their textures, and the fupply- 

 ing of vegetable matter to them. 



And it is found, that in the thinner or lighter calcareous 

 foils, clay, or clayey marie, and the vegetable recrements 

 depofited and obtained in wet or fwampy fituations, may 

 be beneficially applied. In thofe of a contrary or heavier 

 nature, the fpreading of fandy or clayey loams, as circum- 

 ftances may require, on them, will be attended with advan- 

 tage, as altering their texture ; and to thefe may be added 

 compofts of various vegetable and animal fubftances, farm- 

 yard manure and afhes ; befides which great attention is re- 

 quifite in breaking up thefe foils at the proper feaion, as, if 

 this operation be deferred till a dry feafon, they become fo 

 bound or hard, that it will be impoffible to work them, 

 until they are foftened by rain, without very great expence 

 both of teams and of labour in other ways. Near London, 

 the ufe of foot and malt-duft has alfo been found highly 

 beneficial in many cafes of thefe kinds of foils. 



Soils of this nature work, and are capable of being im- 

 proved very differently, according as they are more or lefs 

 heavy. The light and mouldering chalky lands readily ad- 

 mit of thefe means of amelioration, while thofe which are 

 of a more heavy and folid quality, allow of them with con- 

 fiderable difficulty and trouble. Some forts of crops are 

 in a great meafure peculiar to thefe forts of foils, as thofe 



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