322 SCIENCE OF AGRICULTURE. Part II. 



simplest and most effectual means of their improvement. It occasionally happens that 

 the surface of a well proportioned soil is thickly covered with peat, with drifted sand, 

 with gravel, or with small stones. Extensive examples of the former occur in Stirling- 

 shire, and of the latter in Norfolk. In such cases, a simple and effectual mode of im- 

 provement consists in removing the superincumbent strata, and cultivating that below. 

 This can seldom be put in practice on a large scale, with such heavy materials as gravel 

 or stones ; but some hundreds of acres of rich alluvial soil, deeply covered by peat, have 

 been bared and cultivated in Flanders moss in Stirlingshire ; an operation commenced by 

 the celebrated Lord Kaimes, (Gen. Rep. (f Scot. App. v. 5.) copied by his neighbors, 

 and continued by his and their successors. The moss is floated off by streams of water, 

 which empty themselves in the Frith of Forth. In this river, by the winds and tides, it 

 is cast on shore in the bays and recesses, impregnated with salt ; and here it ingenders 

 vegetation on the encroaching surfaces of sand and gravel. Coatings of sand or gravel 

 can seldom be removed on a scale of sufficient extent for agriculture, but have, in some 

 instances, for the purposes of gardening. Sometimes this improvement may be effected 

 by trenching down the surface, and raising up a stratum of better earth. 

 . 2133. Incineration' The chemical changes which can be effected in soils by inciner- 

 ation are considerable. TTiis practice was known to the Romans, is more or less in use 

 in most parts of Europe, is mentioned as an approved practice by our oldest agricultural 

 writers, and has lately excited some degree of attention from the successful experiments 

 of different cultivators. (Farmer's Magazine, 1810 to 1815, and Farmer's Journal^ 

 1814 to 1821.) 



2134. The theory of burning soils is thus given by Sir H. Davy. It rests, he says, 

 entirely on chemical doctrines. The bases of all common soils are mixtures of the 

 primitive earths and oxide of iron ; and these earths have a certain degree of attraction for 

 each other. To regard this attraction in its proper point of view, it is only necessary to 

 consider the composition of any common siliceous stone. Feldspar, for instance, contains 

 siliceous, aluminous, calcareous earths, fixed alkali, and oxide of iron, which exists in one 

 compound, in consequence of their chemical attractions for each other. Let this stone be 

 ground into impalpable powder, it then becomes a substance like clay ; if the powder be 

 heated very strongly, it fuses, and on cooling forms a coherent mass similar to the original 

 stone ; the parts separated by mechanical division adhere again in consequence of chemical 

 attraction. If the powder is heated less strongly, the particles only superficially combine 

 with each other, and form a gritty mass, which, when broken into pieces, has the characters 

 of sand. If the power of the powdered feldspar to absorb water from the atmosphere 

 before, and after the application of the heat, be compared, it is found much less in the 

 last case. The same effect takes place when the powder of other siliceous or aluminous 

 stones is made the subject of experiment, and two equal portions of basalt ground into im- 

 palpable powder, of which one half had been strongly ignited, and the other exposed only 

 to a temperature equal to that of boiling water, gained very different weights in the same 

 time when exposed to air. In four hours the one had gained only two grains, whilst the 

 other had gained seven grains. When clay or tenacious soils are burnt, the effect is of 

 the same kind ; they are brought nearer to a state analogous to that of sands. In the 

 manufacture of bricks the general principle is well illustrated ; if a piece of dried brick 

 earth be applied to the tongue, it will adhere to it very strongly, in consequence of its 

 power to absorb water ; but after it has been burnt, there will be scarcely a sensible ad- 

 hesion. 



21 35. The advantages of burning are that it renders the soil less compact, less tenacious 

 and retentive of moisture ; and when properly applied, may convert a matter that was 

 stiff, damp, and in consequence cold, into one powdery, dry, and warm, and much 

 more proper as a bed for vegetable life. 



2136. The great objection made by speculative chemists to paring and burning, is, that 

 it destroys vegetable and animal matter, or the manure in soil ; but in cases in which 

 the texture of its earthly ingredients is permanently improved, there is more than a com- 

 pensation for this temporary disadvantage. And in some soils where there is an excess 

 of inert vegetable matter, the destruction of it must be beneficial ; and the carbonaceous 

 matter remaining in the ashes may be more useful to the crop than the vegetable fibre 

 from which it was produced. 



2137. Three specimens of ashes from different lands that had undergone paring and 

 burning were examined by chemical analysis. The first was from a chalk soil, and 200 

 grains contained 80 of carbonate of lime, 11 gypsum, 9 charcoal, 15 oxide of iron, 

 3 saline matter, sulphate of potash, muriate of magnesia, with a minute quantity of ve- 

 getable alkali. The remainder alumina and silica. Suppose 2660 bushels to be the 

 common produce of an acre of ground, then, according to this calculation, they would 

 give 172,900 lbs,, containing carbonate of lime 691,60 lbs., gypsum 9509*5., oxide of 

 iron 12,967-5., saline matter 2593*5., charcoal 7780*5. In this instance there was un- 

 doubtedly a very considerable quantity of matter capable of being active as manure pro- 



