analogous to the last, and of which the value may be estimated from the quantity of azote which they severally contain. This value once determined, every farmer knows the quantity which he must lay upon his land; and he thus proceeds upon a much more rational foundation than when he takes for his guide one or other of those vague and arbitrary indications that have been given. Sinclair, for example, would have us lay on nine bushels of feather rubbish to the acre, and Schwertz recommends from four to five times as much more. Nothing, in fact, is more arbitrary and uncertain than to estimate such materials by the bulk; it must be obvious that the weight of a bushel of hide-trimmings, of horn-shavings, and of feather-rubbish, must differ very widely, not only with reference to one another, but also according to the state of division in which each is measured. As a general rule, it is by weight, and weight alone, that the quantity of manure must be estimated.

Shells and mud from the sea-shore and the bottoms of rivers, are matters that are not often very highly azotized; nevertheless they may contain an equivalent of the all-important element, azote, which may bring them near to wet farm-yard dung in point of value. The abundance of such matters in certain situations makes them extremely useful. The alkaline and earthy salts, which they generally contain in considerable quantity, also add to their fertilizing properties. The sea-sand which is employed in Brittany under the name of marl, (merl,) consists, in great part, of the remains of corallines, madrepores, and shells, mixed with a few hundredths of highly azotized organic manner. This marine marl is found in great abundance at the mouths of the river of Morlaix, where there is a considerable traffic carried on in the article. It is said to be reproduced, new banks of it being met with from time to time. It is obtained by dredging from barges, and the process is only allowed to go on from the 15th of May to the 15th of October, when the quays of the town of Morlaix are seen covered with the produce. It is carted to a distance of five leagues inland. A barge-load weighing seven tons, sells at from 6s. 6d. to 8s. This same species of marl is now obtained upon the coast of Plancourtrez and in the roads of Brest. It has also been discovered near the mouth of the river Quimpert. It appears, finally, that the shell sand so much employed by the farmers of Devonshire and Cornwall is of the same essential nature.

In the neighborhood of Morlaix, from five to six tons per acre of this calcareous sand are employed upon light dry soils; from eleven to twelve tons are given to clayey lands. This quantity would probably be too great for porous and damp soils, inasmuch as seamarl belongs to the class of warm manures; that is to say, it under goes speedy decomposition. There can be no doubt that sea-marl acts further, in virtue of the calcareous matter which it contains, and also of its merely mechanical properties upon the strong argillaceous lands of Brittany, for which sand alone is an excellent improver. It is also to the carbonate of lime which it contains, that its good effects upon lands that show an inflorescence of iron pyrites

must be ascribed. It is well to lay this shell-marl upon the land shortly after it is taken from the sea; by long exposure to the air, it suffers disaggregation and loses a portion of its good qualities.

There is another kind of sea-sand called trez, which forms banks in the neighborhood of Morlaix, and which is known under the name of tanque on the northern shores of France, which is favorable to vegetation, particularly after it has been washed and freed from the greater part of the salt which it contains. It is thrown upon the land in larger quantity than the marl. The small quantity of animal matter which it contains putrefies and is lost when it remains exposed to the air for any length of time, so that a distinction has been made between fresh or live trez, and old or dead trez, the one being the article as it comes from the sea, the other after it has been exposed some time on the shore; the article which has been exposed undoubtedly contains a smaller quantity of organic matter than that which is quite fresh. This variety of sea-sand is particularly available upon close and clayey lands, which sometimes receive as many as sixteen tons per acre with advantage; lighter lands, of course, require much less.

Shells, sand, slime, and sea-weed, are not the only useful materials supplied to agriculture by the sea; fish, or their offal, is frequently employed as manure. The practice of manuring with fish is very old, and is universal wherever it can be had recourse to. I have already had occasion to say, that at the period of the conquest of America, the Spaniards found it established among the Indians, on the shores of the Pacific ocean. The lands are occasionally manured with fish along the sea-board of Great Britain and Ireland, and the low lands of Lincolnshire, Cambridgeshire, and Norfolk, also receive occasional supplies of the same powerful manure. The offal of the herring fishery, of cod, of skate, and of the pilchard, in Cornwall, the dog-fish entire, and other kinds, that are either less esteemed, or that are caught in quantities greater than can be consumed as food, are all admirable manures. We have been recommended to mix the fish or fish-offal with quick-lime; but, unless in certain circumstances, the practice is very questionable; the addition is probably only proper where the materials are exceedingly oily, as is the case with pilchards, herrings, &c.: an earthy soap is then formed which prevents the injurious effects upon vegetation which wholly oleaginous matters scarcely fail to produce. One analysis of codfish, which I made along with M. Payen, gave us a proportion of azote of nearly seven per cent. This, of itself, is enough to explain wherefore the flesh, the cartilages, and the bones of fishes should be found such energetic manures.

The slime deposited by rivers also yields manure which may be employed to much advantage. The Nile, which periodically inundates the plains of Lower Egypt, owes its fertilizing action to the slime which it contains, and which it deposites before it again recedes into its bed. On the banks of the Durance, the mud or slime deposited by the river is carefully collected for distribution over the fields in its vicinity. The waters of this river are frequently turbid and

improper for irrigation, until they have deposited the slime which they hold in suspension; the waters are therefore turned into canals for the purpose of deposition before they are let upon the land; and such is the quantity of slime that is precipitated, that two or three gatherings of it are made in the course of the year. It is dug out and thrown upon the banks to dry; reduced to powder, it is fit to be laid upon the land; and such is its fertilizing power, that a field which yielded but four for one, has been brought to yield twelve for one by its means.*

Wood and coal soot, and Picardy ashes. Soot has been known for a long period as a useful manure. M. Braconnot, in the soot of a chimney where wood had been the fuel, found the following ingredients:

The analysis which M. Payen and I made of wood and coal soot, confirms the presence of the azotized principle detected by M. Braconnot. A considerable trade is carried on in soot for agricultural purposes in large towns; it is thrown upon clovers and young wheats, in the proportion of about 20 bushels to the acre. Some have recommended that it should be mixed with lime; but as soot always contains salts having a base of ammonia, the practice is evidently objectionable, unless indeed the object be to get rid of that which is most useful in the article, which will be effectually accomplished by adding lime to it. The proper procedure is to employ the soot without admixture during calm or wet weather. In Flanders, the colewort beds destined for transplanting are very generally manured with soot, which is believed to have the property of preserving the young plants from the attacks of insects. In the neighborhood of Lisle, they give from 55 to 60 bushels of soot per acre. Schwertz appeals to many facts which go far to satisfy us that the effects of soot upon clovers are particularly advantageous; he says, moreover, that coal soot is preferable to wood soot. The superior properties of coal soot are evidently due to two causes: first, it is more dense

* Belleval, in Annals of French Agriculture, 2d series, vol. xiv. p. 261. The beds of many of the oozy-bottomed rivers in England near the sea are inexhaustible sources of the most valuable manure. The bed of the Thames, between London Bridge and Putney Bridge at low water, is a true gold mine if it were but rightly used.-ENG. ED

than wood soot, and in a given bulk actually contains a larger quan tity of matter; secondly, I have found that, for equal weights, coal soot contains the larger quantity of azote.

Picardy ashes are prepared by the slow and imperfect combustion of the pyritic turf which is dug up in the department of the Aisne for the manufacture of sulphate of iron and of alum. This turf piled up, heats, and finally takes fire; the combustion continues for about a month, abundance of sulphureous vapors being disengaged. The residue is a gray ash, still containing a quantity of carbonaceous matter, which is found very advantageous in the way of top-dressing for meadows. It might be maintained that the utility of such ashes depends solely on the sulphate of lime which they contain ; but it is ascertained that they are much more active as manure than this substance employed by itself; analysis, in fact, explains in some degree the fertilizing powers of these ashes, by showing that they contain more than 1 per cent. of azote, to say nothing of the saline matters of which vegetables are so greedy. It is extremely probable that during the slow incineration of the turf, there is a quantity of sulphate of ammonia produced.

The ashes which remain after the lixiviation of the pyritic and aluminous lignites which are mined for the purpose of making green vitriol, are analogous to Picardy ashes, and are employed with equal success in agriculture. At Forges-les-Eaux, the pyritic earths after lixiviation are mixed with a quarter of their weight of turf ashes, and form an active manure which is employed very extensively in the country around the town of Bray in France: it is equally adapted to meadows and to land under roots, such as potatoes or turnips, green crops or corn. Analysis shows these ashes to have the folowing composition:

The vitriolic ashes of Forges-les-Eaux are more highly azotized than those of Picardy; they contain 2.72 per cent. of azote.

The effect of the imperfect combustion of these pyritic turfs, the product which results from it, explains to a certain extent the beneficial effects of the practice of paring and burning, an important and widely spread practice, the utility of which it would be difficult to understand, were it not connected in some way with the production of ammoniacal ashes.

The useful effects of paring and burning, are, in all probability, connected with the destruction of organic matter, very poor in azotized principles; in the transformation of the surface of the soil into a porous, carbonaceous earth, made apt to condense and retain the ammoniacal vapors disengaged during the combustion; lastly, by the production of alkaline and earthy salts, which are familiarly known to exert a most beneficial influence upon vegetation. These

conditions seem so entirely those, the object of which it is to realize by paring and burning, that in order to make the operation favorable to the soil which undergoes it, the vegetable matter which it has produced, must of necessity be transformed into black ashes; when it goes beyond this, as Mr. Hoblyn has well observed, when the incineration is complete, and the residue presents itself as a red ash, the soil may be struck with perfect barrenness for the future. The burning, therefore, that was not properly managed, that led to the complete incineration of all the organic matter, would, for the same reason, have a very bad effect in the preparation of the Picardy ashes; which might indeed act in the same way as turf ashes from the hearth and oven, but which, deprived of all azotized principles, would not ameliorate the ground in the manner of organic manures.

I have frequently seen the process of burning performed in the steppes of southern America. Fire is set to the pastures after the grass which covers them has become dry and woody; the flame spreads with inconceivable rapidity, and to immense distances. The earth becomes charred and black; the combustion of those parts that are nearest to the surface, however, is never complete; and a few days after the passage of the flame, a fresh and vigorous vegetation is seen sprouting through the blackened soil, so that in a few weeks the scene of the desolation by fire, becomes changed into a rich and verdant meadow.

ANIMAL EXCREMENTS.

Horse-dung. The composition of horse-dung would lead us to infer that its action must be more energetic than that of cow-dung. Nevertheless, agriculturists frequently consider it as of inferior quality. This opinion is, even to a certain extent, well founded. Thus although it be acknowledged that horse-dung covered in before it has fermented, yields a very powerful manure, it is known that in general the same substance, after its decomposition, affords a manure that is really less useful than that of the cow-house. This comes entirely from the fact that the droppings of the stable, by reason of the small quantity of moisture they contain, present greater difficulties in the way of proper treatment than those from the cow-house. Mixed with litter and thrown loosely upon the dung-hill, horse-dung heats rapidly, dries, and perishes: unless the mass be supplied with a sufficient quantity of water to keep down the fermentation, and the access of the air be prevented by proper treading, there is always, without the least doubt, a considerable loss of principles, which it is of the highest importance to preserve. I can give a striking instance of this fact in the changes that happen in the conversion of horsedung into manure in the last stage of decomposition: fresh horsedung in the dry state contains 2.7 per cent. of azote. The same dung laid in a thick stratum and left to undergo entire decomposition, gave a humus or mould, from which, reduced to dryness, no more than one per cent. of azote was obtained. I add, that by this fermentation or decomposition, the dung had lost nine tenths of its weight.