resisted its action. Besides, the effect of manures, which have been entirely decomposed, is almost momentary, lasting but for a single season; whilst those which are employed before arriving at this state, continue to exert an influence for several years. In this last case, the decomposition, retarded by the separation of the manures into small portions, continues to go on gradually in the earth, and thus furnishes vegetation with its necessary aliments for a long

time.

The excrements of animals, formed by the digestion of their food, have already undergone a decomposition which has disorganized the principles of their àliments, and in a greater or less degree changed their nature. The strength of the digestive organs, which varies in each species of animal, the difference of food, and the mixture of the digestive fluids furnished by the stomach, modify these manures to a very considerable extent.

The excrements of some animals, as of pigeons, fowls, &c., are employed without undergoing any new fermentation, because they consist mostly of salts, and contain but few juices. Fields are often manured with the excrements of sheep, collected in sheep-folds, or scattered, as in parks, by the animals themselves upon the soil; but in general, the dung of horses and of horned cattle is made to undergo a new fermentation before being applied as manure.

The most general method of producing the fermentation of the dung of quadrupeds, is, in the first place, to form upon the ground of sheep-folds and stables, a bed of straw or of dry leaves. This bed is covered with the solid excrements of the quadrupeds, and impregnated with their urine. At the end of fifteen days or a month, it is carried to a place suited for fermentation, and there formed anew, care being taken every day to spread upon it litter and the scattering of the racks. The formation of these beds, contributes much to the healthfulness of the stables and to the cleanliness of the animals. When from a scarcity of straw, the beds cannot be made of sufficient thickness, or renewed often enough, a layer may be formed of limed gravel, broken fine, and covered with straw. These earths will imbibe the urine, and when they are penetrated by it may be carried into the fields to be buried in the soil. The nature of the earth, upon which beds are formed in sheep-folds of stables, should vary according to the character of the soil which is to receive them, because, by attention to this, the soil may be improved as well as manured. For argillaceous and compact earths, the layers should be formed of gravel and the remains of lime mortars; whilst those of fat marl or of clayey mud should be reserved for light and dry soils.

In some countries, where good husbandry is much attended to, the floors of the stables are paved and slightly sloping, so that the urine flows off into a reservoir, where it is fermented with animal and vegetable substances, and used to water the fields at the moment when vegetation begins to be developed.

The art of fermenting dungs with litter is still very incomplete

in some parts of France. In one place, they let it decay till the straw is completely decomposed; in another, they carry it off into the field as soon as it is taken from the stables. These two me thods are equally faulty. By the first, nearly all the gases and nutritive juices are dissipated and lost; by the second fermentation, which can take place only in masses, will be but very imperfectly carried on in the fields, and the rains can convey to the plants only that portion of the nourishment afforded by the manure, which they can obtain by a simple washing.

The most useful art perhaps in agriculture, and that which requires the most care, is the preparation of dung-heaps. It requires the application of certain chymical principles, which it is not necessary for me to explain, since it is sufficient to point out to the agriculturist the rules by which he should be governed in his proceedings, without requiring of him an extensive knowledge of the theory upon which they are founded.

Solid substances, whether animal, vegetable, or mineral, do not enter into plants unless they are previously dissolved in water, or are drawn with that fluid in a state of extreme division.

Animal and vegetable substances which are in their nature insoluble in water, may, by being decomposed, form new soluble compounds, capable of furnishing nourishment for plants.

Animal and vegetable substances deprived by the action of water of their soluble particles, may in the course of their decomposition form new compounds susceptible of being dissolved. Of this I have given instances in speaking of mould.

That which renders the art of employing dungheaps difficult, in proportion as it is useful, is, that some methods which are adopted occasion a loss of a part of the manure. In fact when the clearings of the farm yard are carried fresh into the fields, and applied immediately to the soil, vegetation is undoubtedly benefitted by the salts and the juices contained in them; but the fibres, the fatness, the oils remain inactive in the earth; and their final decomposition is slow and imperfect. If, on the contrary, the collections of the farm-yard be heaped up in a corner of it, the mass will speedily become heated, corbonic acid gass will be evolved, and afterwards carburetted hydrogen, ammonia, azote, &c. A brown liquid, of which the color deepens gradually almost to black, moistens the heap, and flows upon the ground around it; all is by degrees disorganized; and when the fermentation is completed, there remains only a residue composed of fibre and some carbon in powder.

In those places where they do not allow fermentation to arrive to this degree of decomposition, they still lose by mismanagement, considerable part of their manure.

The most common method is, to deposite in a corner of the farmyard the dung and litter, as it is drawn from the stables, adding to the mass every time these are cleared, and allowing it to be fermented till the period of sowing arrives, whether it be in spring or autumn, when it is carried upon the fields requiring it.

This method prevents many imperfections. In the first place, several successive layers being formed, no two of them can have undergone the same degree of fermentation; in some it will have gone on for six months, and in others but for fifteen days. In the second place, the heap, being exposed to rains, will by frequent washings, have parted with nearly all its salts and soluble juices. In the third place, the extractive portions of the lower and central parts of the mass, the mucilage, the albumen, and the gelatine, will be entirely decomposed; and, lastly, those gases which nourish plants, if developed at their roots, will have escaped into the air; and Davy has observed, that by directing these emanations beneath the roots of the turf in a garden, the vegetation was rendered very. superior to that in the vicinity.

How long should dung-hills be allowed to ferment, and what methods ought to be pursued in forming them. This question leads us to cast a glance upon the nature of the dunghills; and it is not till after having ascertained the difference amongst them, that it can be answered.

The principal parts of vegetables which are employed as manure contain mucilage, gelatine, oil, starch extractive matter, and often albumen, acids, salts, &c. with an abundance of fibrous matter, insoluble in water.

The different substances afforded by animals, including all their excretions, are gelatine, fibrine mucus, fat, albumen, urea, uric and phosphoric acids, and some salts.

The greatest part of the substances, constituting animals and vegetables, are soluble in water; and it is evident that in that state they can be employed as manures without previous fermentation, but it is necessary, that those which contain much insoluble matter should be decomposed by fermentation, because by that process their nature is changed, and they form new compounds, which being capable of solution, can pass into the organs of plants.

Messeurs Gay-Lussac and Thenard have obtained by an analysis of the woody fibre oxygen hydrogen, and especially more carbon, than from any other part of the plant, and they have determined their several proportions; we know that fermentation carries off much carbon; it is then evident, that by causing the fermentation of the vegetable fibre, the principle which forms its distinguishing characteristic will be gradually diminished, and that it will no longer be a body insoluble in water. It is in this manner that woody plants and the dryest leaves are converted into manures.

But as all the solid parts of plants contain fibres which cannot be rendered soluble in water, but by a long period of fermentation; and as it is in the fibre that carbon, a principle so necessary to vegetation, chiefly exists, the fermentation of plants is indispensable to the procuring of the best part of their manure.

The custom of appropriating some crops whilst green to the manuring of the ground, may be perhaps objected to; but I have observed that in that case the plants are buried in the earth at the

time of flowering; and whilst they are succulent, and their fibres soft, and but little formed; and that that warmth and the action of water in the earth, was sufficient to decompose them: this would not take place if the stalks were dried and hardened by the formation of the grain.

The dung of quadrupeds may be mixed advantageously with the earth, at the time of being taken from the stable, if it contain no litter, but if it does, it appears to me better to cause it to undergo a slight fermentation, in order to dispose the straw or leaves of which it is composed in order to become manure.

It is necessary, in producing the fermentation of dung and litter, to use certain precautions by which the inconvenience arising from the usual mode may be avoided.

Instead of heaping up in large masses the collections of the barnyard and stables, and allowing them to run uncovered, and exposed to the changes of the weather, they should be placed under a shed, or be at least protected from the rain by a roof of straw or heath. Separate layers should be formed of each clearing of the stables, cow-house, and sheep-pens. These layers should be from a foot and a half to two feet in thickness; and when the heat produced in them by fermentation, rises in the centre to more than 95 degrees, or when the mass begins to smoke, it should be turned, to prevent decomposition from going too far.

Fermentation should be arrested as soon as the straw contained in the heap begins to turn brown, and its texture to be decomposed. To do this the mass may be spread, or carried into the fields, to be immediately mixed with the soil; or there may be mixed with it mould, plaster, turf, sweepings, &c.

When the dung is not of the usual consistency, as is the case of neat cattle during the spring and autumn, it ought to be employed immediately, as I have already stated; but if it be impossible to apply it to the fields while recent, it should be mixed with earths or other dry and porous substances which may serve as manures for the fields destined to receive it.

Upon nearly all our farms the dung of quadrupeds is exposed to the open air, without the protection of a shed, as soon as it is removed from the stables; and is thus washed by the rains, which carry off all the salts, urine, and soluble juices, and form at the foot of the mass a rivulet of blackish fluid, which is either wholly evaporated or lost in the ground. In proportion as fermentation advances, new soluble combinations are formed, so that all the nutritive and stimulating principles of the dung gradually disappear, till there remain only some weak portions of the manure, intermingled with stalks of straw which have lost all their goodness.

To remedy as much as possible an abuse so injurious to agriculture, it is necessary at least to dig a deep ditch to receive all the juices which flow from the dunghill in order that they may be used in the spring upon the common grass lands; or they may be preserved to water the grass lands with, after the first mowing. A large

cask fixed upon a small cart, and which can be filled by means of a hand pump, is sufficient for this purpose. Beneath the tap of the cask must be fitted a narrow chest about four feet long, with the bottom pierced with holes, through which the liquor may be scattered. This mode of watering, when used after mowing, produces wonderful effects upon the crops the following year.

Before deciding upon the question, whether dung and litter should or should not be made to ferment, it is necessary to take into consideration the nature of the soil to be manured. If this be compact, clayey, and cold, it is better that fermentation should not have taken place, as two effects will be produced by the application of the manure in an undecomposed state. In the first place it will improve the soil by softening and dividing it, so as to render it permeable by air and water; and in the next place it will, whilst undergoing the successive processes of fermentation and decomposition, warm the soil. If, on the contrary, the soil be light, porous, calcareous, and warm, the thoroughly fermented manure, or short muck, as it is called by farmers, is preferable, because it gives out less heat, and instead of opening the earth, already too porous, to the filtrations of water, it moderates the flow of that fluid. Long experience has made these truths known to observing practical far

mers.

When it is required to apply dung to any particular kind of soil, it is necessary that it should be used according to a knowledge of its qualities. The dung of animals bearing wool is the warmest; next, that of horses; whilst that of cows and oxen contains the least heat of any.

Soft or fluid animal substances change the most easily; and the progress of their decomposition is rapid in proportion to the diminution of the quantity of earthy salts contained in them. Their decomposition produces an abundance of ammonial gas. This circumstance distinguishes them from vegetable substances; the decomposition of which gives rise to the production of that gas, only as far as they contain a small portion of albumen. It is particularly to the developement of ammonial gas, which, combined with gelatine, passes into plants, that we can attribute the wonderful effect produced upon vegetation by certain dry animal substances, of which we shall speak presently.

Next to the dung of animals, of which I have just spoken, the urine of horned cattle and of horses is the most abundant manure which can be used in agriculture, and it is not without regret that I see every day so little pains taken to collect it. I have already observed that in those countries where agriculture is conducted with the most ease and skill, all the stables are floored, and the bottoms of them gently sloping, so as to conduct all the urine into a reservoir, where the remains of rape-seed, flax, wild cabbage, human excrements, &c. &c. are thrown into it to undergo fermentation. In the spring, when vegetation begins to be developed, this fermented liquor is carried into the field to water the crops.