the uses of rural economy. The use of coal tar has also been advised for the dead on the battle field.

Dumas added that having often sought an explanation of these facts he had found it in the fact illustrated by Schoenbein that the vapor of turpentine when mixed with air produced an abundance of ozone. He thought that the vapor of coal tar oil might equally ozonize the air. In this case the odorous mixtures would be immediately burned by the ozonized oxygen and the putrid odor rapidly destroyed.

If coal tar really produces this action it is necessary, according to Dumas, to distinguish three effects. 1st, the destruction of the infectious vapor or gas by means of ozone arising from coal tar. 2d, the action of the plaster in preventing the production of new infectious gases by the solidification of the liquids present. 3d, the point of arrest set to the development of putrefactive process by any of the products contained in coal tar, and especially the phenic acid which in the smallest traces in the form of phenate of soda secures the preservation of animal matters in free air.

On the odors of perfumes.-On occasion of the discussion which we have just recorded, Mr. Chevreul offered his ideas upon the mode of action of odoriferous substances. This discussion was intended to recall the publications which this distinguished chemist has made during the past thirty years-researches made specially to trace odors to their material causes. He reviews in the following manner the action by which bodies exert their odors when properly mixed with other odoriferous materials. 1st. Bodies themselves odorant disguise the odors of other substances, as a strong light overpowers a feeble one. 2d. Bodies being themselves odoriferous act in the manner of an acid in neutralizing a base. 3d. Solid bodies may act by capillary affinity to absorb odors, as is the case for example with charcoal. 4th. Other bodies act by altering the constitution of the odorant substance, producing new compounds either odorless or nearly so. Such is the action of moist chlorine or oxygenated water. 5th. Lastly, the action may be two-fold, as in the case of chlorine and ammonia, decomposing one portion and neutralizing the other without decomposition.

Neutralization includes the largest class of cases; thus the volatile odorous acids are neutralized by alkalies to form odorless salts. Ammonia loses its odor when united to an acid. The odors in such cases are truly neutralized, since displacing the acids liberates again the odors each in its own character. Examples of the destruction of odors are numerous and well known to chemists. Sulphydric acid, for instance, is at once decomposed by chlorine and consequently disinfected. Ammonia by the action of chlorine offers an example of both neutralization and destruction of odors, because at the same time we have decomposition of one part of the base and the neutralization of another part by the chlorohydric acid formed.

M. Chevreul proposes to define odors by means of a scale, analogous to our notation of sounds, or for gradations of color by the chromatic diagram (which last device we also owe to this savant). The great obstacle to this plan is the difficulty of employing the sense of smell as we employ that of sight or hearing, a difficulty much increased by the toleration which the smell soon acquires to odors-becoming 'blase.'

In 1830 he endeavored to take account of the changing odors exhaled by the woad vats during evaporation, if possible to define exactly the kind of odor appropriate to each condition of the vat. He reached no positive results although he detected in the dye stuff bath five perfectly distinct odors; the odor of ammonia, a sulphurous odor, a metallic odor, an aromatic odor, clinging for many months to the woolen stuffs which had passed through the woad vat, and lastly, the odor of a volatile acid analogous to that of animal matters in decomposition. M. Chevreul hoped to detect in these odors of the dye vats symptoms to guide the dyer in his art, as the physician finds new indications in his knowledge of symptoms depending on the chemical nature of organic solids and liquids, if these symptoms can be certainly recognized by their odor. Thus he did not shrink from exposing himself to the most repulsive odors of the organism to reach his results. Having often heard the odor of a cancer spoken of as characteristic he examined it and recognized it to a compound of 1st, an ammoniacal odor turning blue a reddened test paper. 2d, a feeble butyric odor. 3d, a heavy odor which is familiar in the 'trying out' of suet or lard. No specific odor exists then in cancers, since the three odors recognized coexist in non-cancerous matters which the disease alters. He recognized these matters in the odor of pus and other products of animal origin, and he also detected in them a sulphurous odor and a smell of fish, due probably to a compound ammonia.

To all these odors he adds what he calls the stale-nauseous (fade nauseabonde) which appears in well-water that has stood some days in a vessel in which have been placed egg shells impregnated with albumen. [We may be permitted to add to these interesting facts some others which we submit to the distinguished author of the chromatic circle and researches on the fatty bodies.

1. If an odorous substance can be neutralized or destroyed by another odorant body there are others destitute of odor which by union produce odorant substances.

(To this class of odorless bodies belong O, S, Se, Te, C, H, As, Az, and we might add P, which is oderless unless combined.)

2. Likewise there are odorless bodies which have become odorant by union with others endowed with odor.

It is thus with oxalic, malic, butyric, racemic, citric, sorbic (the acid recently discovered by Hoffmann), boric, silicic acids, all odorless, which however produce with the elements of alcohol, ethers more or less aromatic.

3. It is necessary to distinguish those bodies which act mechanically on the olfactory membranes (e. g., CIH, FIH, BrH, IH, and the vapors of NO,+HO, SO,HO) from those which exert a physiological influence (for example, Cl, Br, I, NO, SO2, the hydrocarbons, the essential oils, &c.).

4. It is necessary also to distinguish bodies having an odor proper, that is, an odor which exists when they form compounds with other bodies (for example, arsenic). The arsenical odor is recognized in AsH3, AsBr3, and in the cacodyl series. Tin is another example. The odor of tin characterizes a large number of stannic compounds. Sulphur: thus SO2SH, S2C, SNH3, SCI, &c., are distinguished by a more or less sulphurous odor.

We might also mention napthaline, benzoin, and other hydrocarbons and organic radicals.

We see that this group of bodies characterized by a peculiar odor, embraces those elements which, like sulphur, arsenic and phosphorus, are destitute of odor, that is, their odor is manifest only in combination. If we examine these phenomena we observe (a) that elementary bodies are usually destitute of odor; (b) that in general the least odorant compounds are oxygen compounds; (c) highly odorant compounds are usually those containing hydrogen. These seemingly singular facts may to a certain extent be explained when we remember that in general chemical compounds become less volatile as they fix oxygen, which by union with hydrogen they become more volatile. But these considerations do not explain all; they do not tell us why CO and CO2 are odorless gases, while C12H, C26H8, C12H6, &c. &c., are odorant.

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Moreover the perfumes properly so called, as musk and the aromatic essences, rose, lemon, orange, bergamot, lavender, &c. are eminently hydrogen compounds. They are not all volatile and some of them may be exposed to the air for years, exhaling odor all the time, with no sensible loss of weight. Among these are the perfumes isolated by Milon in 1856.* The cause of odors is not referable exclusively to the phenomena of volatility, although as a general thing the odor of most bodies is developed when they are volatilized.

Hydrogen must be considered, par excellence, the exciting cause of odors. This element possesses above all other substances the peculiar property of developing odors even with odorless bodies, as N, C, Se, Te, P, &c., and a great number of compounds, of these and other elements.

Oxygen on the other hand appears to act the chief part in the perception of odors; it seems indeed proved that odors are not recognizable where there is not oxygen in the air to bathe the olfactory membranes.]

Humboldt Foundation.-[After mentioning this foundation, of which we give a more detailed notice on a subsequent page of this volume, our correspondent adds:-] We remark that this foundation resembles the Society for Aiding the Friends of Science, with this difference, that the Humboldt Foundation proposes particularly to aid rising talent and to encourage scientific explorations, while the Society for the Friends of Science sustains scientific men in declining health and comes to the relief of their widows and orphans. The two organizations are therefore complementary to each other, and are worthy to go on side by side.

Photography by Carbon. Concours for the prize founded by the Duke of Luynes. We have for some years past discussed this photographic question-the object of a prize established by a distinguished amateur, the Duke of Luynes. It is required to discover a method by the use of carbon alone, neglecting salts of gold, silver, and other metals, to produce photographs, this being the only material which submitted to the test of time has transmitted to us without change records almost 3000 years old. The Concours has been held; but unfortunately the Commission of the Photographic Society, to whom it was referred, are unable to announce a full success and the trial has been adjourned for three years.

*This Journal, July, 1856, p. 109.

Many persons contested the prize. The desideratum is to obtain a coating of carbon in a manner analogous to that from silver or gold, namely, by reduction. But chemistry as yet has failed to discover a process for the reduction of carbon compounds, and photographers have resorted to animal black which they have applied in any convenient manner to plates previously exposed to the sun. We give a résumé of the new results in two memoirs esteemed by the Commission worthy of reward.

Messrs. Garnier and Salmon, the authors of one of these memoirs, cover the surface of paper with a film obtained from an intimate mixture of bichromate of ammonia and albumen. This coating is dried by heat and exposed to the sun in a frame covered by a glass positive. The picture appears in a yellow-brown tint which becomes more intense by a gentle warmth. The sheet thus prepared is fixed on a planchette and covered with finely powdered ivory-black, the coating being made even by a stump of cotton. It is next detached and plunged in common water, the image uppermost, and there gently moved at intervals for a quarter of an hour. The water is then drawn off and the picture served in a bath composed of 5 parts of concentrated sulphurous acid diluted in 100 parts of water, moving it about as before at intervals. After this double pro cess the carbon almost entirely disappears from the lights and clear spaces, while it remains in quantities proportional to the greater or less intensity of action of the light upon the other portions, and thus the proof finally reproduces the positive, but not perfectly, since the lights and half tints are not pure and the blacks lack somewhat of brilliancy and perfectness. But the process is simple and good; it remains only to perfect it.

M. Pouncy, another competitor, operates a little differently, but obtains results equally satisfactory. His process differs in applying the carbon before exposure of the proof to light, the sensitive coating being formed at once, of bichromate of potassa, gum arabic and finely divided carbon, exposed not under a positive but under a negative plate. On removal the plate is placed in a bath of pure water; after five or six hours immersion he washes under a cock of common water and the carbon positive is obtained.

In this process the manipulation is a little easier and more simple. The use of a negative authorized the expectation of a better result, but the exposure is longer than in the mode of Garnier and Salmon, whose use of a positive avoids the chances of accident which attend the tive plates in the hands of the operator.

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Messrs. Pouncy, Garnier and Salmon share the prize with Mr. Poiterin, who has the merit of anticipating these photographers, whose methods are only an advance on the process which Mr. Poiterin published in 1856.

Transformation of cellulose into sugar.-We have already spoken in this Journal of the plan of Pelouze for facilitating the experiment of Braconnot-the transformation of cellulose into sugar-by exposing the woody fibre and dilute acid to high pressure and heat. It is known, and the fact is recognized by M. Pelouze himself, that this idea has been some years since put in practice both by Mr. Weil and also by Mr. Tribouillet, who obtained a patent for the process.

* This volume, page 126.

Transformation of cellulose into parchment or parchment-paper.-It appears that this curious product of the action of concentrated sulphuric acid on bibulous paper, by which means the paper is changed to a tissue very much resembling ordinary parchment, nearly as strong and resisting the action of boiling water, which parchment does not. It appears that this is not a new observation, but was first made known in 1846 by Messrs. Poumarêde and Figuier in the Journal de Chemie et de Pharm. for 1847, under the name of papyrine. This product however was prepared by aid of an acid of less concentration than is used for parchmentpaper and consequently it did not possess all the desirable properties belonging to vegetable parchment, which is susceptible of a multitude of important applications.

Acclimation. The Dromedary imported into South America.—On the 21st of June last the ship "Splendide" of Marseilles sailed from the port of Algiers for Brazil, having on board fourteen camels (four males and ten females) selected and purchased by the Society for Zoological Acclimation (Societé Zoologique d'Acclimation) to the order of the Brazilian government; this government having decided to test the acclimation of these animals in the sandy provinces of Brazil. Several of these provinces, particularly Céara, during many months of the year are destitute of water, and much resemble in physical characters those regions of Africa and Asia where the camel and dromedary are so eminently serviceable.

The Society of Acclimation, in view of the importance of the case, have sent one of the Vice Presidents of the society, M. Richard (du Cantal), a distinguished zootechnist, to Algeria, between Boghar and Lagonat, in a region inhabited by one of the tribes most distinguished for the number and beauty of their dromedaries. From these herds Richard selected ten females of three to four years old, three males of four years, and one of seven, all in the highest condition, at a cost of 380 francs each. Four Arab camel drivers were also obtained to accompany the animals.

The July (1859) number of the Journal of Acclimation relates all the history of this experiment, to which we refer for the details. But it is to be remarked as regards the prospect of success for this enterprize that a similar experiment has met with success some time since in Texas and Central America, the credit of which is due to Major Wayne of the United States Army.

BIBLIOGRAPHY.-There has appeared from the central book depot of Agriculture at Paris

Dictionnaire raisonné d'Agriculture et d'Economie du Bétail par le Dr. Richard, du Cantal, 2 vol. in 8vo.-Richard is one of the Vice Presidents of the Society for acclimation spoken of above. He is best known for his intimate knowledge concerning domestic animals and especially of what in France is called Zootechny. The two volumes of his Dictionary are filled with his observations on this important agricultural question.

MALLET-BACHELIER, quai des Augustines, Paris, has publishedRecherches sur les Météores et sur les lois qui les régissent par Coulvier Gravier. 1 vol. in 8vo, with numerous plates.-Mr. Coulvier Gravier has brought out in this volume the fruit of forty years of observations on the state of the heavens. We have often found occasion to mention his ob