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ing quotation from Professor Rennie, furnish strong confirmation of some of the opinions which I have endeavored to maintain. It will however be left, without farther comment, for the reader to observe the accordance, and to make the application.

"HUMIC ACID AND HUMIN.-In most chemical books the terms Ulmic Acid and Ulmin are used, from Ulmus, elm; but, as its substance occurs in most, if not all plants, the name is bad. I prefer Sprengel's terms, from Humus, soil.

is in general as entirely deficient in the soils of Virginia, as that ingredient has heretofore been supposed by agricultural writers, to be common in all soils: and

2nd. That notwithstanding this total absence of the carbonate of lime, that lime in some other form of combination, in greater or less quantities, is an ingredient of every soil capable of producing vegetation.

Nor do these facts come in conflict with each other; nor either of them with the position which This important substance was first discovered by Klaproth, in a sort of gum from an elu; but it has been contended for, that calcareous matter in has since been found by Berzelius in all barks; by proper proportions is necessary to cause fertility in soils. Should some other person, who may be M. Braconnot in saw-dust, starch, and sugar; and aided by sufficient scientific light, undertake the what is still more interesting for our present pur-investigation, he may supply all that is wanting pose, it has been found by Sprengel and M. Poly- for the full proof of this theory of the cause of dore Boullay, to constitute a leading principle in fertility, by showing that the value of a soil (under soils and manures. Humin appears to be formed equal circumstances) is in proportion to the quanof carbon and hydrogen, and the humic acid of humin and oxygen. Pure humin is of a deep soil. The direct and positive proof of this doctify of the vegetable salt of lime present in the blackish brown, without taste or smell, and water trine, I confidently anticipate will hereafter he obdissolves it with great difficulty and in small quan- tained from more full examinations of the humic tities; consequently it cannot, when pure, be available as food for plants. acid, and its compounds in various soils, and from kinds of those ingredients, and of the rate of correct and minute reports of the quantities and natural fertility of each soil. As yet, however interesting the recent discovery of humic acid may suspected it to have any thing like the important be to chemists, it does not seem that they have bearing on the fertilization of soil, which I had attributed to the supposed acid principle or ingre

Humic acid however, which I may remark, is not sour to the taste, readily combines with many of the substances found in soils and manures, and

not only renders them, but itself also, easy to be dissolved in water, which in their separate state could not take place. In this way humic acid will combine with lime, potass, and ammonia, in the form of humates, and the smallest portion of these will render it soluble in water and fit to be taken up by the spongelets of the root fibres.

dient.

Supposing the doctrine to be sufficiently proved, in different soils, according to the views which it may be useful to trace the formation of acidity have been presented, and to display the promise which that quality holds out for improving those soils, which it has hitherto rendered barren and worthless.

It appears to have been from ignorance of the important action of the humic acid in thus helping to dissolve earthy matters, that the older writers were so puzzled to discover how lime and potass got into plants; and it seems also to be this, chiefly, which is so vaguely treated of in the older books, under the names of extractive, vegetable extract, calcareous earth in sufficient quantity to produce Every neutral soil at some former time contained mucilaginous matter, and the like. Saussure, for the uniform effect of that ingredient of storing up instance, filled a vessel with turf, and moistened it and fixing fertility. The decomposition of the thoroughly with pure water, when by putting ten successive growth of plants left to rot on the rich thousand parts of it by weight under a heavy soil, continually formed vegetable acid, which press, and filtering and evaporating the fluid, he slowly and gradually united with the lime in the obtained twenty-six parts of what he termed ex- soil. At last these two principles balanced each tract; from ten thousand parts of well dunged and other, and the soil was no longer calcareous, but rich kitchen garden mould, he obtained ten parts became neutral. Instead of its former ingredient of extract; and from ten thousand parts of good carbonate of lime, it was now supplied with a vecorn field mould, he obtained four parts of extract. getable salt of lime. This change of soil does not M. Polydore Boullay found that the liquid ma-effect the natural growth, which remains the same, nure, drained from dung hills, contains a large pro-and thrives as well as when the soil was calcaportion of humic acid, which accounts for its fer-reous-and when brought into cultivation, the soil tilizing properties so well known in China and on is equally productive under all crops suited to the continent: and he found it also in peat earth, calcareous soils. If the supplies of vegetable matand in varying proportions in all sorts of turf. It

appears probable, from Gay-Lussac having found ter continue, the soil may even become acid in a similar acid, (technically Azumic acid,) on de-of sorrel-but without losing any of its fertility some measure, as may be evidenced by the growth composing the prussic acid, (technically Hydro- before acquired. The quantity of acidity in any cyanic acid,) that the humic acid may be found in soil frequently varies: it is increased by the growth animal blood, and if so, it will account for its utility of such plants as delight to feed on it, and by the as a manure for vines, &c. Dobereiner found the decomposition of all vegetable matters. Hence the longer a poor field remains at rest, and not

gallic acid convertible into the humic,”

But without the aid of this recent discovery of grazed, the more acid it becomes-and this evil the humic acid, if the foregoing examinations of keeping pace with the benefits derived, is the soils, and the arguments which follow remain un-cause why so little improvement, or increased proquestioned, these two remarkable and important facts may be considered as established:

1st, That calcareous earth, or carbonate of lime,

duct, is obtained from putting acid soils under that mild treatment. Cultivation not only prevents new supplies, but also diminishes the acidity al

ready present in excess, by exposing it to the at-out remuneration, and without suspecting that mosphere-and the more a soil is exhausted, the more will its acidity be lessened.

their worst virgin land was then richer than their manured lots appeared to be. The cultivator of We have seen from the proof furnished by the such soil, who knows not its peculiar disease, has analysis of wood ashes, that even poor acid soils no other prospect than a gradual decrease of his contain a little salt of lime, and therefore must always scanty crops. But i the evil is once unhave been slightly calcareous at some former time. derstood, and the means of its removal within his But such small proportions of calcareous earth were reach, he has reason to rejoice that his soil was so soon equalled, and then exceeded, by the formation constituted as to be preserved from the effects of of vegetable acid, before much productiveness was the improvidence of his forefathers, who would caused. The soil being thus changed, the plants have worn out any land not almost indestructible. suitable to calcareous soils died off, and gave place The presence of acid, by restraining the producto others which produce, as well as feed and thrive tive powers of the soil, has in a great measure on acidity. Still, however, even these plan's fur- saved it from exhaustion; and after a course of nish abundant supplies of vegetable matter, suffi- cropping which would have utterly ruined soils cient to enrich the land in the highest degree: but much better constituted, the powers of our acid the antiseptic power of the acid prevents the leaves land remain not greatly impaired, though dormant, from rotting for years, and even then, the soil has and ready to be called into action by merely being no power to profit by them. Though continually relieved of its acid quality. A few crops will reduce wasted, the vegetable matter is always present in a new acid field to so low a rate of product, that abundance; but must remain almost useless to the it scarcely will pay for its cultivation-but no great soil, until the accompanying acidity shall be de-change is afterwards caused, by continuing scourgstroyed.

ng tillage and grazing, for fifty years longer. Thus our acid soils have two remarkable and opposite qualities, both proceeding from the same cause: they cannot be enriched by manure, nor impoverished by cultivation, to any great extent. Qualities so remarkable deserve all our powers of investigation: yet their very frequency seems to have caused them to be overlooked-and our writers on agriculture have continued to urge those who seek improvement to apply precepts drawn rom English authors, to soils which are totally different from all those for which their instructions were intended.

CHAPTER VIII.

EARTH IN SOILS.

It may well be doubted whether any soil destitute of lime in every form, would not soon become a perfect barren, incapable of producing a spire of grass. No soil thus destitute is known, as the plants of all soils show in their ashes the presence of some lime. But it is probable that our subsoils, which when left naked by the washing away of the soil, are so generally and totally barren, are made so by their being entirely destitute of lime in any form. There is a natural process regularly and at all times working to deprive the subsoil of all lime, unless the soil is abundantly supplied. What constitutes soi', and makes the strong and plain mark of separation and distinction between the more or less fertile soil and the absolutely steril subsoil beneath? The most obvious cause for this difference which might be stated, is the THE MODE OF OPERATION OF CALCAREOUS dropping of the dead vegetable matter on the surface: but this is not sufficient alone to produce the effects, though it may be when aided by another cause of more power. When the most barren soil was formed or deposited by any of the natural agents to which such effects are attributed by geologists, it seems reasonable to suppose that the surface was no richer than any lower part. If then a very minute proportion of lime had been equally distributed through the body of poor soil to any depth that the roots of trees could penetrate, it would follow that the roots would in the course of time take up all the lime, as all would be wanting for the support of the trees: and their death and decay would afterwards leave all this former ingredient of the soil in general, on the surface. This process must have the effect, in the course of time, of fixing on and near the surface Chemistry has taught that silicious earth, in any the whole of a scanty supply of lime, and on leaving the subsoil without any. But if there is withi: state of division, attracts but slightly, if at all, any the reach of the roots more lime than any one crop of the parts of putrescent animal and vegetable or growth of plants need, then the superfluous matters. But even if any slight attraction really lime will be permitted to remain in the subsoil, exists when the earth is minutely divided for exwhich will then be improvable by vegetable sub-periment in the laboratory of the chemist, it canstances, and readily convertible to productive soil. not be exerted by silicious sand in the usual form The manner in which lime thus operates, will be explained in the next chanter.

Nearly all the woodland now remaining in Lower Virginia, and much of what has long been arable, is rendered unproductive by acidity, and successive generations have toiled on them with

PROPOSITION 3. The fertilizing effects of cal careous earth are chiefly produced by its power of neutralizing acids, and of combining putrescent manures with soils, between which there would otherwise be but little, if any, chemical attraction. PROPOSITION 4. Poor and acid soils cannot be improved durally, or profitably, by putrescent manures, without previously making them calcareous, and thereby correcting the defect in their constitution.

It has already been made evident that the presence of calcareous earth in a natural soil causes great and durable fertility: but it still remains to be determined, to what properties of this earth its peculiar fertilizing effects are to be attributed.

in which nature gives it to soils-that is, in particles comparatively coarse, loose, and open, and yet each particle impenetrable to any liquid, or gaseous fluid that might be passing through the va

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cancies. Hence, silicious earth can have no pow-earth also exerts some chemical power in attracter, chemical or mechanical, either to attract en-ing and combining with manures, but too weakly riching manures, or to preserve them when actu-to enable a clay soil to become rich by natural ally placed in contact: and soils in which the qualities of this earth greatly predominate, must give out freely all they have received, not only to a growing crop, but to the sun, air, and water, so as soon to lose the whole. No portion of putrescent matter can remain longer than the completion of its decomposition-and if not arrested during this process, by the roots of living plants, all will escape in the form of gas, into the air, without leaving a trace of lasting improvement. With a knowledge of these properties, we need not resort to the common opinion that manure sinks through sandy soils, to account for its rapid disappearance.*

*

means. For though clays are able to exert more force than sand, in holding manures, their closeness also acts to deny admittance beneath the surface to the enriching matters furnished by the growth and decay of plants: and therefore, before being brought into cultivation, a poor clay soil would derive scarcely any benefit from its small power of combining chemically with putrescent matters. If then it is considered how small is the power of silicious and aluminous earths to receive and retain putrescent manures, it will cease to cause surprise that such soils cannot be thus enriched, with profit, if at all.

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I shall offer some reasons for believing that the powers of attracting and retaining manure, possessed by these two earths, differ greatly in force.

Davy states that both aluminous and calAluminous earth, by its closeness, mechanically careous earth will combine with any vegetable exexcludes those agents of decomposition, heat, air tract, so as to render it less soluble, and consequentand moisture, which sand so freely admits; and ly not subject to the waste that would otherwise therefore clay soils, in which this earth predomi- take place, and hence "that the soils which connates, give out manure much more slowly than "tain most alumina and carbonate of lime, are sand, whether for waste or for use. The practical" those which act with the greatest chemical eneffect of this is universally understood—that clay ergy in preserving manures." Here is high ausoils retain manure much longer than sand, but re-thority for calcareous earth possessing the power quire much heavier applications to show as much which my subject requires, but not in so great a effect at once. But as this means of retaining degree as I think it deserves. Davy apparently manure is altogether mechanical, it serves only places both earths in this respect on the same footto delay both its use and its waste. Aluminous ing, and allows to aluminous soils retentive powers equal to the calcareous. But though he gives evExcept the very small proportions of earthy, sa- idence (from chemical experiments) of this powline and metallic matters that may be in animal and er in both earths, he does not seem to have invesvegetable manures, the whole balance of their bulk tigated the difference of their forces. Nor could (and the whole of whatever can feed plants,) is com- he deem it very important, holding the opinion posed of dinerent elements, which are known only in which he elsewhere expresses, that calcareous the forms of gases-into which they must be finally re-earth acts "merely by forming a useful earthy insolved, after going through all the various stages of fermentation and decomposition. So far from sink-gredient in the soil," and consequently attributing ing in the earth, these final results could not be possito it no remarkable chemical effects as a manure. bly confined there, but must escape into the atmosphere as soon as they take a gaseous form, unless immediately taken up by the organs of growing plants. It is probable that but a small portion of any dressing Our aluminous and calcareous soils, through the of manure remains long enough in the soil to make whole of their virgin state, have had equal means this final change-and that nearly all is used by grow-of receiving vegetable matter; and if their powers ing plants, during previous changes, or carried off by for retaining it were nearly equal, so would be air and water. During the progress of the many their acquired fertility. Instead of this, while the changes caused by fermentation and decomposition, every soluble product may certainly sink as low as the calcareous soils have been raised to the highest rains penetrate: but it cannot descend lower than the condition, many of the tracts of clay soil remain water, and that, together with the soluble manure, will the poorest and most worthless. It is true that be again drawn up by the roots of plants. One excep- one labored under acidity, from which the other tion, however, seems probable. Should the soil need was free. But if we suppose nine-tenths of the draining, to take off water passing beneath the surface, vegetable matter to have been rendered useless by the soluble manure might be carried off by those springs; that poisonous quality, the remaining tenth, apand this supposed result receives strong confirmation plied for so long a time, would have made fertile, from the complete loss of fertility which is often observed in spots over a foundation that is springy in wet any soil that had the power to retain the enriching matter. seasons, but which have been kept under tillage, without being drained. We are as yet but little informed Many kinds of shells are partly composed of geas to the particular changes inade, and the various new latinous animal matter, which I suppose, must be substances successively formed, and then decomposed, chemically combined with the calcareous earth, during the whole duration of putrescent manures in and by that means only is preserved from the puthe soil-and no field for discovery would better re-trefaction and waste that would otherwise certainly ward the investigations of the agricultural chemist. For want of this knowledge we proceed at random in using manures, instead of being enabled to conform to any rule founded on scientific principles: nor can we hope so to manage manures with regard to their fermentation, the time and manner of application, mixing with other substances, &c., as to enable the crops to seize every enriching result as soon as it is produced, and to postpone as long as possible the final results of decomposition-which ought to be the ends sought in every application of putrescent manure.

and speedily take place. Indeed, the large proportion of animal matter which thus helps to constitute shells, instead of making them more perishable, serves to increase their firmness and solidity. When long exposure, as in fossil shells, has destroyed all animal matter, the texture of the calcareous substance is greatly weakened. A simple experiment will serve to separate and make manifest to the eye, the animal matter, which is thus combined with and preserved by the calcareous

earth. If a fresh water muscle shell is kept for some days immersed in a weak mixture of muriatic acid and water, all the calcareous part will be gradually dissolved, leaving the animal matter so entire, as to appear still to be a whole shell-but which when lifted from the fluid which supports it, will prove to be entirely a flaccid, gelatinous, and putrescent substance, without a particle of calcareous matter being left. Yet this substance which is so highly putrescent when alone, would have been preserved in combination with calcareous matter, in the shell, for many years, if exposed to the usual changes of air and moisture-and it secured from such changes, would be almost impe

rishable.

this combination as fast as they require it, and as easily as from sand. The means then by which calcareous earth acts as an improving manure, are, completely preserving putrescent manures from waste, and yielding them freely for use. These particular benefits, however great they may be, cannot be seen very quickly after a soil is made calcareous, but will increase with time, and with he means for obtaining vegetable matters, until their accumulation is equal to the soil's power of retention. The kind, or the source, of enriching manure, does not alter the process described. The natural growth of the soil, left to die and rot, or other putrescent manures collected and applied, would alike be seized by the calcareous earth, and fixed in the soil.

This, the most important and valuable operation of calcareous earth, gives nothing to the soil-but only secures the other manures, and gives them wholly to the soil. In this respect, the action of calcareous earth on soils, is precisely like that of mordants in "setting" or fixing colors. When alum, for example, is used by the dyer for this purpose, it adds not the slightest tinge of itself-but it holds to the cloth, and also to the otherwise fleeting dye, and thus fixes them permanently together. Without the mordant, the color might have been equally vivid, but would be lost by the first wetting of the cloth.

Calcareous earth has power to preserve those animal matters which are most liable to waste, and which give to the sense of smell full evidence when they are escaping. Of this, a striking example is furnished by an experiment which was made with care and attention. The carcass of a cow that was killed by accident in May, was laid on the surface of the earth, and covered with about seventy bushels of finely divided fossil shells and earth, (mostly silicious,) their propositions being as thirty-six of calcareous, to sixty-four of silicious earth. After the rains had settled the heap, it was only six inches thick over the highest part of the carcass. The process of putrefaction was so slow, that several weeks passed before it The next most valuable property of ealcareous was over; nor was it ever so violent as to throw off manures for the improvement of soil, is their powany effluvia that the calcareous earth did not inter-er of neutralizing acids, which has already been cept in its escape, so that no offensive smell was incidentally brought forward in the preceding chapever perceived. In October, the whole heap was ter. According to the views already presented, carried out and applied to one-sixth of an acre of our poorest cultivated soils contain more vegetable wheat-and the effect produced far exceeded that matter than they can beneficially use-and when of the calcareous manure alone, which was ap- first cleared, have it in great excess. So antisepplied at the same rate on the surrounding land. tic is the acid quality of poor woodland, that before No such power as this experiment indicated (and the crop of leaves of one year can entirely rot, two which I have repeated in various modes, and al- or three others will have fallen-and there are always with like results,) will be expected from ways enough, at any one time, to greatly enrich clay. the soil, if the leaves could be rotted and fixed in Quicklime is used to prevent the escape of of it, at once.* The presence of acid, by preventing fensive effluvia from animal matter; but its opera- or retarding putrefaction, keeps the vegetable tion is entirely different from that of calcareous matter inert, and even hurtful on cultivated land; earth. The former effects its object by "eating" and the crops are still further injured, by taking up or decomposing the animal substance, (and nearly the poisonous acid, with their nutriment. A sufdestroying it as manure,) before putrefaction be- ficient quantity of calcareous earth mixed with gins. The operation of calcareous earth is to such a soil, will immediately neutralize the acid, moderate and retard, but not to prevent putrefac- and destroy its powers: the soil, released from its tion-not to destroy the animal matter, but to pre-baneful influence, will be rendered capable, for the serve it effectually, by forming new combinations with the products of putrefaction. This important operation will be treated of more fully in a subsequent chapter.

first time, of exerting the fertility which it really

*The antiseptic effect of vegetable acid in our soils The power of calcareous earth to combine with receives some support from the facts established with regard to peat soils, in which vegetable acids have and retain putrescent manure, implies the power been discovered by chemical analysis: and though the of fixing them in any soil to which both are ap- peat or moss soils of Britain differ entirely from any soils plied. The same power will be equally exerted if in this country, still some facts relating to the former the putrescent manure is applied to a soil which class, may throw light on the properties of our own had previously been made calcareous, whether by soils, different as they may be. Not only does vegetanature, or by art. When a chemical combination ble matter remain without putrefaction in peat soils is formed between the two kinds of manure, the and bogs, and serve to increase their depth by regular one is necessarily as much fixed in the soil as the accessions from the successive annual growths, but other. Neither air, sun or rain, can then waste even the bodies of beasts and men have been found the putrescent manure, because neither can take it unchanged under peat, many years after they had been covered. [Aiton's Essay on Moss Earth. It is well from the calcareous earth, with which it is chemi-known that the leaves of trees rot very quickly on the cally combined. Nothing can effect the separation of the parts of this compound manure, except the attractive power of growing plants-which as all experience shows, will draw their food from

rich limestone soils of the western states, while the successive crops of several years' growth may be always found on our acid woodland, in the different stages of their slow decomposition.

possessed. The benefit thus produced is almost | dry on the surface, the part made calcareous will immediate: but though the soil will show a new still show the moisture remaining, by its darker vigor in its earliest vegetation, and may even dou- color. All the effects from this power of calcable its first crop, yet no part of that increased pro-reous manures may be observed within a few years duct is due to the direct operation of the calcareous after their application-though none of them so manure, but merely to the removal of acidity. strongly marked, as they are on lands made calThe calcareous earth, in such a case, has not made careous by nature, and in which, time has aided the soil richer in the slightest degree, but has and perfected the operation. These soils present merely permitted it to bring into use the fertility great variety in their proportions of sand and clay it had before, and which was concealed by the yet the most clayey is friable enough, and the acid character of the soil. It will be a dangerous most sandy, firm enough, to be considered soils error for the farmer to suppose that calcareous of good texture: an they resist the extremes of earth can enrich soil by direct means. It destroys both wet and dry seasons, better than any other the worst foe of productiveness, and uses to the soils whatever. Time, and the increase of vegegreatest advantage the fertilizing powers of other table matter, will bring those qualities to the same manures-but of itself it gives no fertility to soils, perfection, in soils made calcareous by artificial nor furnishes the least food to growing plants.

These two kinds of action are by far the most powerful of the means possessed by calcareous earth, for fertilizing soils. It has another however of great importance-or rather two others, which may be best described together as the power of altering the texture and absorbency of soils.

means.

The subsequent gradual accumulation of vegetable matter in soils to which calcareous manures have been applied, must also aid the improvement of their texture and absorbing power. The vegetable matter also darkens the color of the soil, which makes it warmer by more freely absorbing the rays of the sun.

cent manures. If the power of fixing manures in soils, has been correctly ascribed to calcareous earth, that alone is enough to show that soils containing that ingredient in sufficient quantity, must become rich-and that aluminous and silicious earths mixed in any proportions, can never form other than a steril soil.

At first it may seem impossible that the same manure could produce such opposite effects on Additional and practical proofs of all the powers soils, as to lessen the faults of being either too san- of calcareous earth will be furnished, when its use dy, or too clayey-and the evils occasioned by and effects as manure will be stated. I flatter both the want, and the excess of moisture. Con- myself however, that enough has already been tradictory as this may appear, it is strictly true as said both to establish, and account for, the differto calcareous earth. In common with clay, cal-ent capacities of soils for improvement by putrescareous earth possesses the power of making sandy soils more close and firm-and in common with sand, the power of making clay soils lighter. When sand and clay thus alter the textures of soils, their operation is altogether mechanical; but calcareous earth must have some chemical action also, in producing such effects, as its power is far greater than that of either sand or clay. A very great quantity of clay would be required to stiffen a sandy soil perceptibly, and still more sand would be necessary to make a clay soil much lighter-so that the cost of such improvement would generally exceed the benefit obtained. Greater effects on the texture of soils are derived from less quantities of calcareous earth, besides obtaining the more valuable operation of its other powers.

Every substance that is open enough for air to enter, and the particles of which are not absolutely impenetrable, must absorb moisture from the atmosphere. Aluminous earth reduced to an impalpable powder, has strong absorbing powers. But this is not the form in which such soils can act—and a close and solid clay will scarcely admit the passage of air or water, and therefore cannot absorb much moisture except by its surface. Through sandy soils, the air passes freely; but most of its particles are impenetrable by moisture, and therefore these soils are also extremely deficient in absorbent power. Calcareous earth, by rendering clay more open to the entrance of air, and closing partially the too open pores of sandy soils, increases the absorbent powers of both. To increase that power in any soil, is to enable it to draw supplies of moisture from the air, in the driest weather, and to resist more strongly the waste by evaporation, of light rains. A calcareous soil will so quickly absorb a hasty shower of rain, as to appear to have received less than adjoining land of different character: and yet if observed in summer when under tillage, some days after a rain, and when other adjacent land appears

The object of this essay is to treat only of calcareous earth (as before defined) as a manure, and not of pure lime, nor of manures in general. Still the nature of that which is properly my subject, is so intimately connected with some other kinds of manures, and is so liable to be confounded with others, which act very differently, that frequent references to both classes have been, and will be again necessary. To make such references more plain and useful, some general remarks and opinions will now be submitted as to the peculiar modes of the operation of various manures, and particularly of lime.

Until now, I have been careful to say but little of pure lime, for fear of my meaning being mistaken, from the usual practice of confounding it with calcareous earth-or of considering its first and later operations, as belonging to one and the same manure. The connexion between the manures is so intimate, yet their actions so distinct, that it is necessary to mark the points of resemblance as well as those of difference.

My own use of lime as a manure has not extended beyond a few acres; and I do not pretend to know any thing from experience, of its first or caustic effects: but Davy's simple and beautiful theory of its operation carries conviction with it, and in accordance with his opinions I shall state the theory, and thence attempt to deduce its proper practical use.

By a sufficient degree of heat, the carbonic acid is driven off from shells, limestone, or chalk, and the remainder is pure or caustic lime. In this state is has a powerful decomposing power on all

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