SOIL. 



rocks, remain very often for ages with only a thin covering 

 of vegetation ; but that foils from the decompofition of 

 limeftone, chalk, and bafaltes, are not unfrequently clothed 

 by nature with the perennial grades, and afford, when 

 ploughed up, a rich bed of vegetation for every fort of cul- 

 tivated plants. 



From what has been faid on the formation of rocky foils, 

 it rnuft. be obvious that they are as various as the rocky 

 matters from which they are produced, and probably much 

 more fo, in confequence of the alterations which have taken 

 place in them, from the continued operation of water, and 

 different other caufes. 



In fo far as the cropping of land is concerned, it mull be 

 evident that no general principle can be laid down for it, 

 unlefs the whole of the circumftances connefted with the 

 nature, compofition, and fituation of the foils, as well as 

 fubfoils, be fully underftood. 



In like manner, in the above writer's opinion, the modes 

 of cultivation in different foils niuit be different ; as the 

 fame praftice that may be excellent in one cafe may be de- 

 ftruftive in others. Thuf, for inftance, deep ploughing 

 may be very advantageous and profitable in rich thick foils ; 

 but in fertile fhallow ones, upon cold clay or fandy fub-foils, 

 very injurious and hurtful. Sihceous fandy foils are much 

 more prodnftive in moiit wet climates, where the fall of rain 

 is great, fuch as thofe in the fouth-weft and north-weft of 

 this country, and in feme places in Ireland, than in dry 

 diRricls ; and in fuch fituations, wheat and beans will re- 

 quire lefs coherent and abforbent foils than in thofe which 

 are drier ; and bulbous-rooted plants will, it is faid, thrive 

 well in foils that have as many as fourteen parts out of fif- 

 teen of fand. The exhaufting powers of crops, too, it is 

 afi'erted, will be influenced by the fame circumftances ; as 

 where fufficient moilture cannot be abforbed by plants, they 

 muft necellarily take up more manure. In the fouth-weltern 

 and north-weilern parts of this ifland, as well as in Ireland, 

 corn will, it is faid, cxhauft lefs than in dry inland dillriAs ; 

 and oats are much more deteriorating, efpecially in dry cli- 

 mates, than in fuch as are moift. In many other inftances, 

 the fame is likewife the cafe. 



In regard to the conftitution or compofition of fertile 

 foils, the firit effential requifite, according to Mr. Kirwan, 

 is, that it contain a fufficient quantity of the three or four 

 fimple earths above mentioned, and of the foluble carbona- 

 ceous principle ; and that the other requifites are, that the 

 proportion of each, and the general texture of the foil, be 

 fuch as to enable it to admit and retain as much water as is 

 neceflary to vegetation, and no more. Alfo, further, that 

 as it has been feen that the retentive powers of moifture are 

 very different in the fimple earths, the proportions in which 

 the fertility of a foil requires them to be mixed mult be dif- 

 ferent in climates and countries that differ confiderably in 

 moifture; in the drier, they muft be fuch as are molt re- 

 tentive ; in the m-'ijler, fucli as fuffer it to pafs or evaporate 

 more eafily. 'I'he lame remark alfo extends to fituation. 

 Lands on a plain Ihould be fo conflitnted, a» to be lefs re- 

 tentive of water than thofe fituated on a declivity ; as has 

 been feen, and is very evident : confeqiiently, lands that 

 have a retentive or impermeable fub-foil, Ihould be differently 

 conflituted from thofe tfiat have one lefs retentive, or more 

 permeable. And the time of the year in which rain moft 

 abundantly falls may alfo be worthy of notice, in adjulling 

 this bufinefs. 



From a variety of fafts and obfervationt, which we can- 

 not minutely detail, it is inferred that in the drier countries, 

 where the fall of rain is but 20 inches, the foil, to be fer- 

 tile, muit be clofcr, and the quantity of calcareous earth 



much increafed, and that of the filiceous earth much dimi- 

 nifhed. Thus, in the climate of Turin, where the fall of 

 rain exceeds 40 inches, the proportion of filiceous earth is 

 from 7710 80/frcwt., and that of calcareous from 9 to 14, 

 to fuffer this excefs of rain more eafily to evaporate. In 

 the chmate of Upfal, where the fall of rain is 24 inches, the 

 proportion of filex is only 56 per cwt., but that of calx 

 is 30 ; and in the climate of Paris, which is ftiil drier, the 

 proportion of filex is only from 46 to 51, and that of calx 

 37.5 per cwt. And hence we may perceive the iieceflity of 

 attending to the average quantity of rain, to judge of the 

 proper conftitution of fertile lands upon fixed principles. 

 The quantity of rain differs much, in different parts of the 

 fame kingdom ; but in general, in Ireland, Mr. Kirwan be- 

 heves it to be between 24 and 28 inches, on an average. 

 In the two laft mixtures, the proportions vary confiderably; 

 the firft may ferve, it is faid, as a model for the heavier 

 foils ; and the fecond for the lighter. In the following 

 experiments, the carbonic principle feems to have been 

 extradted from the furrounding garden-mould, with which 

 the pots communicated, by means of their perforation at 

 the bottom. 



The author of a late work on " Agricultural Chemiitry" 

 ftates, that as plants have no locomotive powers, they can 

 only grow in places where they are fupplied with food ; and 

 that the foil is neceflary to their exifteiice, both as affording 

 them properly the means of nourifhment, and enabhng 

 them to fix themfelves in fuch a manner as to obey thofe 

 mechiinical laws, by which their radicles are kept below the 

 furface, and their leaves expoled to the free atmofphere. 

 That as the fyftems of roots, branches, and leaves, are very 

 different in different vegetables, fo they ffourifh molt per- 

 fedtly in different foils fuited to them : the plants that have 

 bulbous roots require a looler and a lighter foil than fuch as 

 have fibrous roots ; and the plants having only fhort fibrous 

 radicles fland in need of a firmer foil than fuch as have tap- 

 roots, or extenfive roots of the lateral kind. 



He found a good turnip foil from Holkham, in the 

 county of Norfolk, to afford eight out of nine parts iiliceout 

 fand ; and the finely divided matter to confift of 



Carbonate of lime 



Sihca 



Alumina . . - 



Oxyd of iron 



Vefjetable and fahne matter 



Moifture - - . 



63 

 15 

 II 



3 

 5 

 3 



A foil particularly fitted for raifing flourilhing oaks, to 

 be conftituted nearly as noticed :sfterwards, below. 



An excellent wheat-foil from near Weft Drayton, in the 

 county of Middlefex, gave three parts in five of fihceous 

 fand ; and the finely divided matter confifted of 



Carbonate of lime - - - - 28 



Silica 3* 



Alumina 29 



Animal or vegetable matter and moifture 1 1 



It is noticed, that of thefe foils, the firft was the leaft^ 

 coherent in texture, and the laft by far the moft fo. In all 

 cafes, the conftituent parts of the foil which irivc tenacity 

 and coiierencc are, it is f.iid, the finely divided matters ; 

 and that they poffefs the power of giving tliofe qualities in 

 the liigheft degree, when they contain much alumina. A 

 fniall quantity of finely divided matter is fufEcient, it is faid, 

 to fit a foil for the produftion of turnips and barley ; and 

 the writer has feen a tolerable crop of tuniips on a foil con- 

 taining 



