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ÀPPLICATIO OF FAlnl-YARD DUNG. f Continued from our last.) A full century has elapsed siiiec Jethro Tull published the idea of pulverisation of the soil being made to supersede the use of dung and though experience has overturned this posi- tion, yet the agricultural world has not at this day reaped above half the benefit of Tull's favourite conception. It is one of the general laws of chemical combination, that its efficacy is in the inverse riltio of the affinity of aggregation for this latter power holds together the homogeneous particles, and prevents their separating and joining the parts of another body; and the greater the power is, the less efficacious must be affinity of composition. All chemical action is combination or union, and decomposition or separation; and light and heat often appear as the new arrangements take place—heat is disengaged, and often absorbed, and a change of temperature' happens. Bodies that have little or no affinity, and do not enter into combination, are made to do so by the addition of one or more substances and this principle shows the necessity of applying a number of substances at one time, and of bringing them into contact with each in a state of minute adherence. Many kinds of chemical action are effected by heat, electricity, and other agencies, over which any control is impossible, and which do not take place from mere mixture and comminution; yet by that process a ready accession of means will be afforded of pro- ducing combinations which in another state of existence of the substances would not have happened. All chemical forces are subordinate to the cause of. life, and to heat and electricity, and to mechanical friction and motion. The latter power is able to change their direction, increase or diminish their ten- dency, and also completely to stop and reverse their action. But causes must exist to produce chemical affinity, or the cycle of life would stand still, and, from our ignorance of these causes and of the application, it is probable that in many cases their action is arrested and stopped, and often rendered useless or not produced at all-or, at least, but accidentally—arising from proceedings not being yet based on definite or measured causes. The effects of manures of every kind depend on the quality of the land to which they are applied, and also on the state of preparation of the soil at the time when the substances come into contact with each other. Finely-pulverised bodies cannot mix with those of a grosser form. Masses, lumps, and clods of homogeneous or heterogeneous substances will lie together And remain in the original state of cohesion or aggregation; but no affinity of composition takes place at sensible" dis- tances, and consequently no results follow from the combined influence of the bodies in union. The contact of a pulverised substance with a mass or any gross formation cannot produce the effects of combination. The finer particles of the former touch only the external surface of the latter, the interior parts remaiuing unaffected and unavailable for the purposes and effects of alteration. Hence the necessity of all substances that are brought into contact being reduced to the same state of minuteness, in order that combination may take place at insensible" distances, and produce an active union from the reciprocal action of the molecules of the two bodies on each other. This affinity of composition is one chief agent in the operations of nature and of art; and the ease and rapidity with which bodies are decomposed, or enter into new combinations, are directly as the quantity of the surfaces "that they present, or inversely as their masses. The efficacy of composition is inversely as the attraction of adhesion the absolute force re- mains the same, but increases on account of the diminution of the opposing attraction. The investigations of science, the results of experience, and the conclusions of observation, unite in forming a powerful argument in favour of reducing to a state of the most minute subdivision possible all bodies that are intended to unite and incorporate with each other, in order to produce by their combined influence the substances, liquid, solid, or ceriform that enter into the organs and structure, and promote the growth of plants. The materials must be applied in the greatest possible number of particles. On this point science is decisive, and nature shows the example of alluvial grounds and deposits, and in fact of all improved cultivation. APPLYING DUNG TO WHEAT.—The operations of life are on the surface of the earth, and the more plausible theory of the food of plants supposes that it is derived as much from the at- mosphere as from the soil. We may also infer that new ele- ments will be produced from the manure and the air, and which may be imbibed by plants. From these grounds I have long been of opinion that the farm-yard dung, which is now Z, laid on the bare fallows for wheat, may be more beneficially applied as a top-dressing in March on the growing plants. At that season the soft lands would not carry the carts to lay the dung on the land; but this difficulty may be removed, by lay- ing moveable railways on the field, along which light waggons would convey the dung to be spread from them on both sides, and which would receive the dung from the carts at the end of the field. The dung being thinly and evenly spread on the land, it may lie from one to two months, and being then har- rowed, it will form a top-dressing for the plants of no common value of the minute particles of dung and soil, and a bed for grass seeds of a kind that they never receive. A matrix of different substances, in a finely reduced and comminuted state, resembles the alluvium" of nature, in which plants so very much delight to grow.—J. D. CLAY Lk-, DS. -The most economical, and by far the simplest and most generally applicable, mode of reducing the cloddy suiface of clay lands, is to lay mounds of alternate layers of the rough materials and hot lime, and to ignite the heaps by exposure to the air, or by the application of water. A heap of 7 yards in length, 4 in width, and 3 feet high, and mixed with 72 bushels of hot lime, has been recommended to be reduced to ashes or nearly so, when clay may be applied as long as suf- Z, ficient heat remains. The damp heat exhaled from the lime will produce a smothering effect on the clay, which is not easily attained in the open air, either with a large or small quantity of flaming combustibles in the former case there is danger of i a' ciiiatioii and uselessness, and in the latter, of im- perfect burning and extinction of the fire from exposure, and the surrounding contact of air. The lime can be got at any time, and the process can go on in wet or dry weather the means are more at the command of the farmer, and the work can be performed more promptly on that account than when it depends on so m-my contingencies, often beyond control. The expense of burning in heaps has been stated at Is. to Is. 6d. per load, and of clod burning at 12s. to 15s. an acre, but little dependence can be placed on such statements, or on the loads that are used, or on the quantity of ashes got from burning an acre of land, as they all vary according to circumstances. The quantity of ashes should be such as will cover the surface -5 U when they are spread; if the quantity be less, the application may be worth little, and a large quantity can be got at less proportional expense than a smaller. This mode of burning by lime is a very simple, an effectual, and a process at all times available, and the ultimate products are a mixture of finely- reduced and pulverised substances to be blended and incorpo- rated with the soil, on which acquisition so very much of the fertility of the earth depends.