The recent progress of science not only confirms this opinion, but also enables us to reply to some objections raised against the generality of the principle; it accounts for the necessity of nitrogen for the development of plants.

The first products of the putrefaction of animal remains and even of dunghills, often the most rich in nitrogen, have lately been regarded as injurious to vegetation: hence the preference which has been given to completely decayed dunghills and to animal matters reduced into mould (terreau) after long alterations.*

On the other hand, admitting the carbon furnished by the carbonic acid of the air and of the manures to be the principal nourishment of plants, the utility of products capable of thus furnishing carbon, and ulmic acid in particular, has lately been appreciated. This theory, also admitted in several scientific works, had led to turf and exhausted mould (terreau) being regarded as excellent fertilising agents, which are, on the contrary, poor manures, at least if they be not modified by the addition of animal matter abounding in nitrogen. Finally, it was doubted whether the nitrogenous products of manures were useful from a stimulant action, or from the production of assimilable compounds.

A concours, opened in 1825 by the Royal and Central Society of Agriculture, effected the solution of the first part of the problem, proving that the most putrescible remains of animals may be applied as manure without any previous decay, with the sole condition of relaxing the effects of the putrefaction, and of thus proportioning the solution and the disengagement of the nitrogenous products to the growth of the plants which should absorb them.

The approbation accorded to this work, with the first prize, has since been sanctioned by a daily increasing practice of the means indicated by the author.t

* At the close of the last century, Bosc, one of our learned agricultural writers, in the article Manure, page 70, of the great Dictionary of Agriculture, said, that in order to employ as manure the flesh of slaughtered animals, it was necessary to allow it to putrefy for several years: but then, it will be understood, the greater part of the nitrogenous products of the putrefaction were thus dissipated in the air.

† A permanent concours has, since then, every year encouraged the application of these means, which have already utilised considerable quantities of blood, muscular flesh, &c., previously wasted in France and other countries.

N. S.-VOL. I.

With regard to the question as to the part which nitrogenous substances may perform in vegetable nutrition, it was in a great measure solved, either by the observation of a general law which assigns to all the young organs of plants, to all their parts endowed with a great activity of development, and to the substances contained in the passages of their ascending sap, an elementary composition rich in nitrogen ;* or by the analytical demonstration of the quantities of nitrogen which plants imbibe from atmospheric air, in so much greater proportions as the soil has been more ameliorated by culture.†

Each of us having thus arrived, by different ways, to the same conclusions, we have been fortunate in finding in the experiments and assent of agricultural writers the confirmation of our views, and it appeared to us beneficial to combine our efforts in order to continue together, and in views of more direct applications, the work at which we had separately labored.

Before giving the results of our analysis, we will present a few general considerations, in order better to define the character and the value of these numerical data, and to explain certain apparent anomalies.

And first, it is important here to call to mind the phenomena of the nourishment of vegetables on account of the structure and physiological actions of their organs, which are accomplished by the absorption of dissolved or gaseous substances. These phenomena are thus found freed from all the complication which results in the animal nutrition from influence relative to the physical state of the aliments swallowed.

The quality and the quantity of manures applicable to plants may therefore vary within very extended limits, if they yield their gaseous or soluble products in suitable proportions, for a given time and surface. It is thus that all other things being equal, a manure entirely decomposable into its soluble and gaseous products, in the course of a great an effect on the first crop as five times single year, will be capable of producing as the quantity of another manure whose ultimate decomposition would be effected only in five years; but the latter will furnish the useful products during five times longer period, and there will be thus a compensa

tion.

The duration of manures, often dependent on the cohesion and insolubility of the or

* Recueil des Savants Etrangers, Vol. VIII. page 163; Memoir on the Chemical Composition of Vegetables.

† Annales de Chimie et de Physique, tome LXVII. page 5, and LXIX. page 353. R

ganic substance, should then be taken into serious consideration. This idea, so useful to agriculturists, also serves to show the concordance which exists between the analytical results of the laboratory and the practical effects of culture in certain cases, in which this agreement appeared doubtful.

It may sometimes be advantageous to modify the manures, either by hastening their decomposition, or by retarding it, in order thus better to proportion their products to the wants of the plants. We will quote a few examples worthy of attention; we will call to mind the favorable conditions which in the residues of refineries, quintuples the effects of blood and the means of disinfection which produce analogous results in their application to matters too readily putrescible. In considering the proximate changes which the animalised matters undergo by putrefaction, we admit that, of all these matters, the most advantageous for the productions of manures are precisely those which can give rise to the largest quantity of soluble or volatilisable nitrogenous bodies. Indeed the presence alone of nitrogen in a matter of organic origin is not sufficient for characterising it as a manure; pit-coal, for example, contains very appreciable quantities of nitrogen, but pit-coal is absolutely without action on land as a manure. This is because this substance cannot undergo by the action of atmospherical agents, that putrid fermentation whose final result is a production of ammoniacal salts and other nitrogenous compounds.

The efficacy of ammoniacal salts in manures is now admitted by chemists who have paid attention to agriculture: their opinion is based on the most authentic and best established practical facts. Thus putrefied urine is, as every one knows, one of the most energetic manures; now the product of the putrefaction of urea is almost entirely carbonate of ammonia.

Guano,-that very active manure, which for ages has fertilised the arid sands of the Peruvian coasts,-is almost entirely formed of salts with an ammoniacal base.

However, in acknowledging the importance, the absolute necessity, of nitrogenous principles in manures, we are far from considering that these principles are the only ones useful in improving the soil. It is certain that various alkaline salts are indispensable to the development of vegetables.

In this respect we regard as aliments the organic and inorganic bodies, which should complete and repair by their decay the congenerous substances in living beings.

The non-nitrogenous organic principles do not, doubtless, act a passive part in the fertilizing action of manures; but, with some few exceptions, the fixed salts, water, or its

elements, and carbon, superabound in the various manures; they constitute the greater part of the stubble and other remains of crops; their excess may even become injurious. The element whose proportions are the weakest is nitrogen. It is also the most rapidly dissipated by the alteration of quaternary organic bodies, an alteration which is useful for exciting the decomposition of non-nitrogenous organic substances. For all these reasons, we regard it as the principle whose presence it is especially important to ascertain; it is its proportion which establishes, in our opinion, the comparative value of manures, and their reciprocal equivalents.

Numerous practical facts have confirmed these scientific data, and the expectations to which they gave rise. It is known that the richest manures, those which now have the greatest mercantile value, and which are brought from the greatest distances, are formed of very nitrogenous substances; such are the membranes of the adipose tissues, the remains of hair, wool, silk, feathers, shavings of horn, and blood, which, dried, represent from 32 to 50 times their weight of normal dung.

Our experiments, described in this memoir, would also indicate the means of obtaining, by collecting certain injurious insects, a new kind of rich manure, whose employment would be doubly profitable to agriculturists.

Certain manures, whose strength has been correctly estimated, contain, it is true, only small proportions of nitrogenous substances, but they are almost completely free from nonnitrogenous organic remains of this number are the organized bodies abundantly encrusted with carbonate of lime, forming immense deposits in the sea, and which, under the denomination of merl, are so much used by the skilful cultivators of the environs of Morlaix.

It is doubtless by supplying the loss of nitrogenous matters in the vegetable remains which are exhausted, that animal manures fertilise the land; the Flemish manure fulfils this part itself every year, and assists in producing abundant crops, without ever leaving the earth inactive. Thus, then, the manures are of so much the greater value as the proportion of nitrogenous organic substance is greater, as this proportion predominates especially over that of the non-nitrogenous organic substances, and as the decomposition of the quaternary substance is gradually operated, and follows better the progress of vegetation.

The results of the numerous analysis to which we have devoted ourselves, and whose details are given in our memoir, apply to 95 substances; they are collected in the two

synoptical tables, in which also figure the elements which have served as the basis of our calculation. The first table presents the experimental data and observations, as well as the strength of the manures compared with dry or humid dung. The second table, freed from all the ciphers of observations, shows, with respect to each substance, two numbers which indicate the equivalents of manures, that is to say, the quantity by weight of each of them equivalent to 100 parts of dung; 1st, in the dry state; 2nd, in the ordinary humid state.

This manure, so generally employed in rural farming, costs from 60 to 75 centimes and even one franc for 100 kilogrammes; a similar dung may be obtained in town at a lower price, especially when the conveyance, effected by vehicles returning from market, costs very little; in this case it amounts from 45 to 60 centimes every one, however, will be able, according to local circumstances, to compare the price of dung with that of each of the other manures.

It is often advantageous to employ fresh dung on more or less compact lands; for its effect is so much the greater as it has undergone less decay; besides, it improves the land by the division which it operates before it is disaggregated.* It is generally admitted, that dung disaggregated by maceration in pits, and, as much as possible, protected from the influences which favor fermentation, presents for light soils a hygroscopic substance, which improves the land, and a useful aliment for vegetation.

The farm-yard dung of which we have been speaking, and which we consider as normal manure, is a mixture of the dung of herbivorous animals and litter: before giving a few details concerning several other mixed composts, we will describe, in particular, the manures arising from the vegetable remains which most commonly enter into its composition.

Straws.

gathering: in this respect the analytical data, which are perfectly in accordance with the practical observations and the facts recently admitted in vegetable physiology, prove that the straws are much the more rich in nitrogenous principles as the seeds of the plant are farther from maturity. We have operated on straw taken at the period conveniently chosen for gathering the ripe seeds, and we analysed recently cut products comparatively with old straw. Finally, we determined separately in some of them the composition of the upper and younger part; it will be remarked, that the latter is much more rich in nitrogen than the lower part nearest to the stubble.

It is known, that generally, in rural farming, a great part of the straw is used for feeding animals, that almost always also a portion is used as litter, and that the latter increases often even beyond the farmer's expectations, especially as the season advances, for the humidity which occasions mouldiness, and the dryness which hardens the straw, render it unfit to be used as food for animals.

In all cases, the straws which have not been sent away nor used for thatching buildings, are conveyed directly or indirectly to the dunghill; and it is useful to be able to compare their value in this respect.

Some, it is true, which have been threshed in the fields, and which are too ligneous to be easily applied to the nourishment of animals, or used as manure, are abandoned or burned; it would often be profitable to cause them to disaggregate by maceration in the liquids of the dunghill, and afterwards to spread them on the land: besides, their strength or richness in nitrogen may serve as a basis for the calculations of writers on agriculture. On looking over the tables, it will be remarked that, considered as manures, the kinds of straw analysed, stand thus: 1, pea straw; 2, straw of lentils; 3, of millet; 4, of buck wheat; 5, of oats; 6, of wheat; 7, of barley; and 8, of rye. The latter, generally obtained on earths of the second class, contains less nitrogen than all the others, and is inferior in quality both as food and manure; but, fortunately, it is preferable for thatching and for other works in straw; it may also be added, that in these applications the small proportions of nitrogenous substances would be rather advantageous in rendering the straw less alterable; that, finally, straws are perceptibly richer in nitrogen when the land on which they are grown have been falsified by abundant manuring.

The husk of wheat, also called small straw,

*Which, completely dried, is equal to the dry substance of farm-yard dung.