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THE FARMER'S MAGAZINE. 



a state of minute subdivision, which settle into a 

 stratum round the roots of the plants, and form 

 the source whence the nutriment is drawn, and 

 which was formed by the application. Hence 

 arises the superiority of earthy substances for the 

 purpose of top-dressing, over the effects of caustic 

 stimulents; the latter exert a passing influence 

 on the growing bodies of the moment, but leave no 

 residuum as a source of future use. 



At a minimum calculation, the expense of a 

 dressing of unmixed chalk cannot be less than £4, 

 or 40 cart-loads at 2s. each. This amount sup- 

 poses a favourable contiguity of the chalk and the 

 land on which it is to be used. When made into 

 composts, the expense will be very similar, as the 

 smaller number of cart-loads per acre will meet 

 the cost of collecting the earths, and of turning 

 over the heaps. In very many situations, the cost 

 will be very considerably above £4, owing to the 

 expense of can-iage, and the quantity of the article 

 that is required to produce any effect. If this 

 quantity be not large, the expense will be wholly 

 lost ; for quantity is most imperatively required in 

 many cases, to rise to a superior affinity. The 

 most important recommendation must not be omit- 

 ted, that all aggregated bodies that are used in top- 

 dressings must be reduced to a finely-pulverized 

 state. Lumps of chalk will lie on the surface of 

 lands without being broken ; the plough and the 

 harrow turn them over, and the roll presses them 

 into the soil ; but the purpose will be entirely de- 

 feated unless the body be finely reduced : well- 

 prepared composts have an advantage in this way. 

 On soils of the lighter description, sands, loams, 

 gravels, and everk on chalky lands, very great im- 

 provements have been done by large applications 

 of chalk, the effects of which have not ceased with 

 a few crops, but have operated, like all calcareous 

 substances, in imparting properties to the land that 

 it did not before possess, and at the same time in- 

 creasing the quantity of every crop. The quantity 

 applied must be large, and when used for top- 

 dressing grass lands, it must be applied one year 

 or more before the land is ploughed, in order to 

 raise a close, grassy sward, which, by its decompo- 

 sition affords the food to future crops. This vege- 

 table stratum in its formation constitutes the value 

 in top- dressings. Chalk is a heavy body, and is 

 not much used, and less in the native locality than 

 at distances to which it is carried. 



Clay. 



Clay is a mixed body, mostly composed of 

 " alumina, sulphuric acid, and water." It is found 

 in vast beds in the alluvial deposit of the tertiary 

 formation, of which chalk, or the most recent 

 condition of lim.e, forms the basis, and is much 

 mixed with other bodies in diflferent states and 

 combinations. The prevailing colour is brown or 

 reddish brown, yellow, and sometimes bluish — 

 sandy, gravelly, often solid, more or less unctuous 

 and soft to the touch, often friable and dry, break- 

 ing into small lumps, containing more silex, and 

 loses its plasticity ; and perhaps no body is found 

 in a greater diversity of composition in soils and in 

 slates, and in all argillaceous formations. It enters 

 mto all good lands, in fertile soils from 9 to 15 per 



cent., and in barren lands from '20 to 40 per cent. : 

 the absence of it forms a soil too dry and porous, 

 and a superabundance of it constitutes a soil too 

 wet and cold when in a moist state, and contracts 

 and hardens by heat into a condition that is adverse 

 to vegetable life. Clay is found calcareous, meagre, 

 and unctuous, effervescing with acids, rough and 

 gritty, and containing a greater quantity of alumina. 

 The purest specimen contains upwards of 60 per 

 cent, of sand, and is always mixed with mineral, 

 animal, and vegetable substances. The aluminous 

 base imbibes 1 5 times its weight of water, and re- 

 tains it with great obstinacy. 



Like all other substances, the quality of the clay, 

 the mode of its combination with other substances, 

 and the exposure of the combined elements, render 

 it a fertilizer both in the simple state and in the 

 condition of a " compost " with other substances. 

 When found of a clammy or indurated texture, 

 great difficulty is experienced in reducing the sub- 

 stance to particles that can act with and upon the 

 other elements with which the contact will occur. 

 But with calcareous clays, the process is easy, the 

 mass is friable and crumbling, and the dissolution 

 is so fine as to allow an intimate incorporation with 

 the soil. Accordingly very great improvements 

 have been effected by excavating clays of this 

 nature, and laying pretty large quantities on the 

 surface of light lands — a moist quality has been 

 given to the sandy soil, and more firmness and a 

 greater consistency. The quantity must be liberal, 

 from 100 to 160 loads an acre, and must be at- 

 tentively used in the breaking and spreading of the 

 pieces. On the other hand, ferruginous clays, 

 and those of a white, sandy, and gravelly nature, 

 are positively pernicious, and require a mixture 

 with substances of a better quality to correct the 

 noxious property, and an exposure to atmospheric 

 action to extract and dissipate the hurtful effluvia. 

 A total alteration must be acted upon the con- 

 stituents before clays of that nature can be made 

 fertile, either as a cultivated soil, or as an applica- 

 tion to other lands. 



Sulphuric acid in any form or combination is 

 noxious to vegetable life, and in preparing clay for 

 the purpose of acting as a manure, that hurtful in- 

 gredient must be banished, and more friendly 

 qualities introduced. The quantity of water and 

 acid amounts to two-third parts of the constituents 

 of pure clay ; and being in combination, the des- 

 truction of both elements must be effected. Some 

 body must be applied that will act violently and 

 forcibly in disintegrating the mass of clay, in sun- 

 dering the particles, in banishing existing pro- 

 perties, and in conferring more valuable qualities 

 by means of reciprocal action and mutual com- 

 binations. For this purpose, no better agent has 

 yet been found than caustic lime, in a state of hot 

 shells newly burned. Lime is the oxide of 

 " calcium," one of the newly discovered terrigenous 

 metals, which contains in lOO parts about 38 parts 

 of oxygen. An oxide is a sour, pungent body, and 

 draws off every volatile substance, without fusing 

 the primitive body : it is the circumstance or state 

 of change, while calcination is the mode of effecting 

 it. By the application of a violent heat, lime loses 

 the water of crystallization, and the carbonic acid 



