the design is of a bold character, it will be reproduced at the distance of a centimetre. The impression is not, then, the result of action of contact, or of chemical action. A coloured engraving of many colours is reproduced very unequally; that is to say, the colours imprint their image with different intensities, varying with their chemical nature-some producing an impression which is very visible, whilst others scarcely tint the sensitive paper.

It is similar with characters printed with different inks. Printers' ink, whether it be such as is used with type or for copper-plate printing, and the ordinary writing ink, formed of a solution of nutgalls and sulphate of iron, do not give images; while certain "English inks give impressions sufficiently strong." Vitrified characters,

traced upon a plate of varnished porcelain, or covered with enamel, are imprinted upon the sensitive paper without the porcelain itself leaving any trace of its presence; but a porcelain not covered with varnish or enamel, such as biscuit china or "la pâte de kaolin,” produces a slight impression.

If, after having exposed an engraving to the light during one hour, we apply it upon a white card which has remained in darkness during some days, and if, after having left the engraving in contact with the card during twenty-four hours at least, we put the card in its turn in contact with a leaf of sensitive paper, we shall have, after twenty-four hours of this new contact, a reproduction of the engraving, a little less visible, it is true, than if the engraving had been applied directly upon the sensitive paper, but yet distinct.

When a tablet of black marble, lightly strewn with white spots, after having been exposed to the light, is applied at once to a sensitive paper, the white parts of the marble only are imprinted upon the paper. Under the same conditions, a tablet of white chalk will produce a sensible impression, while a tablet of charcoal will produce no such effect. When a black and white feather has been exposed to the sun, and applied in darkness to a sensitive surface, the white parts alone imprint their image. The feather of a parrot-red, green, blue, and black-has given scarcely any impression, acting as if the feather had been black. Certain colours, however, have left traces of a very feeble action.

Experiments have been made with textile fabrics of different natures and of various colours. The following are a few of the results:

Cotton-White impressed the sensitive paper

Brown (by madder and alumina). Nothing given.

Violet (by madder, alumina, and iron). Scarcely anything.
Red (by cochineal). Nothing.

Turkey Red (by madder and alum). Nothing.

Prussian Blue, upon white ground, is the blue which pro

duces the best impression.

Blue (by indigo). Nothing.

Chamois (by peroxide of iron). No impression.

Linen, silk, and woollen cloths give equally different impressions, according to the chemical nature of the colours.

* The millimetre is 0.03937 of an English inch. The centimetre is 0·39371 of an English inch.

M. Niépce calls particular attention to the following experiment, which is, as he says, curious and important :

We take a tube of metal-of tin-plate, for example, or of any other opaque substance-closed at one of its extremities, and cover the interior with paper or white card: the open end of the tube is exposed for about an hour to the direct rays of the sun. Then apply this open end to a sheet of sensitive paper, and preserve it in this state for twenty-four hours, when the circumference of the tube will have designed its image. More than this. If an engraving upon china paper is interposed between the tube and the sensitive paper, we find the same reproduced. Reproduced, be it remembered, by the radiations which have been absorbed and re-developed from the interior of the tube. "If we close the tube hermetically as soon as we cease to expose it to the light, we shall preserve, during an indefinite time, the faculty of radiation, which the insulation has communicated, and we shall see that this is manifested by the impression produced when we apply the tube upon a sensitive paper, after having removed the cover by which the tube was closed."

Niépce then informs us, that he has repeated upon images formed in the camera-obscura similar experiments to those which he has made with the direct light. A piece of card which had been kept in darkness was placed in the camera-obscura for about three hours, and on it was projected an image brilliantly illuminated by the sun. Then the card was applied to sensitive paper, and after twenty-four hours there was obtained a reproduction of the primitive image of the camera-obscura. There must be a long exposure to obtain an appreciable result.

It will be remembered that some few years since Professor Stokes drew attention to some peculiar conditions of light, to which he gave the name of fluorescence. M. Niépce has made several experiments with substances which possess this peculiar property. A design was traced upon a sheet of white paper with a solution of sulphate of quinine, one of the most fluorescent bodies: the paper was then exposed to the sun, and subsequently applied to the sensitive paper. The fluorescent parts were reproduced in black, much more intense than that of the paper upon which the design was formed. A plate of glass interposed between the design and the sensitive paper prevented any impression. A plate of glass, coloured yellow by the oxide of uranium, produced the same effect. If the design in sulphate of quinine has not been exposed to light, nothing is produced upon the sensitive paper. M. Niépce then tells us that a design traced with phosphorus upon paper will, without being exposed to light, impress very rapidly the sensitive paper. This impression is, beyond all doubt, due to the formation of phosphide of silver-it is a chemical change quite independent of the luminous effect, and has nothing in common with the other phenomena. He says, however, that the same effects are produced by fluate of lime, rendered phosphorescent by heat.

Such are the principal matters to which M. Niépce now directs attention; and if his results are confirmed by further experiments, they must materially change our views of luminous variations.

211

Natural History.

ZOOLOGY.

VIVIPARITY AND OVIPARITY.

AT the American Association (Albany) Meeting, Professor Agassiz has made a communication on Viviparity and Oviparity, on which his researches in embryology have thrown great light. At one time it was believed that those animals which brought forth their young alive had peculiarities which indicated exclusive relationship. The progress of embryology had proved that there was no such relationship, and no radical difference between viviparous and oviparous animals. In the family of snakes there were viviparous and oviparous genera. The vipers brought forth their young alive, but they were not on that account like quadrupeds. Among quadrupeds, too, the marsupials, when first born, were carried about by the mother, attached to the nipple, until they were capable of being again born, and, as it were, standing on their own legs. Placental connexion between mother and young was of not much consequence. Sharks showed that some being oviparous, others viviparous, with or without placental connexion. Yet the mode of development in all was precisely the same, and was a shark development. There was nothing in it which was allied to that of birds. This had a decided influence on classification. There was no reason for separating the marsupials from other mammals. In each group and different class the relation between the modes of development indicated the real relations of the animals. Animals which were developed in the same manner were sure to be found in the end to belong to the same general division. He maintained that the distinctions founded on complications of structure must be given up for general classification, and confined to the minor distinctions.-Edinburgh New Philosophical Journal, No. 10.

NEW FACTS OF TRANSFUSION.

DR. BROWN-SÉQUARD has presented to the French Academy of Sciences a paper, in which he tries to prove the two following propositions:-1st. That arterial or venous blood, from an animal of any one of the four classes vertebrata, containing oxygen in sufficient quantity to be scarlet, may be injected, without danger, into the veins of a vertebrated animal of any one of the four classes, provided that the amount of injected blood be not too considerable. 2nd. Arterial or venous blood of any vertebrated animal, being sufficiently rich in carbonic acid to be almost black (noirâtre), cannot be injected in the veins of a warm-blooded animal without producing phenomena of asphyxia, and most frequently death, after violent convulsions, provided that the quantity of injected blood be not below one five-hundredth weight of the animal, and also that the injection be made not too slowly. Dr. Brown-Séquard states that

he has transfused into the jugular vein of dogs without any ill effect, blood of rabbits, guinea-pigs, cats, cocks, hens, pigeons, ducks, turtles and tortoises, frogs and eels. In rabbits and birds he has also transfused blood of other animals without any marked bad effect. He attributes chiefly to carbonic acid the phenomena which had been considered as due to differences in the blood of various species. In many communications to the "Société de Biologie," the same physiologist has related facts to prove that in the experiments of Blundell, of Dieffenbach, and of Prevost and Dumas, there were many causes of failure unknown to these experimenters which have prevented them from re-establishing life permanently in dogs bled to death, and transfused with blood from animals of another species. These causes of failure were- -1st, that too much blood was transfused at once; 2nd, that the blood was not fresh; 3rd, that it did not contain oxygen enough, and contained too much carbonic acid. Dr. BrownSéquard has ascertained that even the blood of birds, defibrinated and rich in oxygen, has been able to re-establish full and durable life in dogs, weighing from 15lb. to 20lb., and having lost more than 16oz. of arterial blood, i.e., more blood than the dogs of Blundell had lost. From 30 to 48 grammes of birds' blood (1oz. to 1 oz.) have been sufficient in many cases to restore full life.—Medical Times.

BREEDS OF DOMESTIC ANIMALS.

A PAPER has been read to the British Association, "On the Dispersion of Particular Breeds of Domestic Animals as connected with the great Ethnological Divisions of Mankind," by Mr. Ogilby. The author commenced by stating that the power of domesticating animals appeared to exercise a great influence on the civilization of mankind. Where men had no cattle to attend to or breed, there they always exhibited the most degraded forms of their race. great object of the paper was to show that certain breeds of sheep had always appeared with particular races of men, and that, at the present day, we had no better guide to the original types of mankind than were afforded by certain races of sheep. The paper was illustrated by maps and diagrams, illustrating the breeds of sheep.

THE HORNS OF ANIMALS.

The

It is commonly believed that the horns of the ox acquire an additional ring every year after the third, but the addition of annuli is far from being annual in other species. Many rings are gained in one year's growth of the ram's horns, and in those of the ringhorned antelope. The length of the horn forms a distinguishing characteristic in some breeds of cattle; but whatever improvements may have been effected in the form and character of the carcase, by the modification of food and habits, it does not appear that we have been able to superinduce any improvement or alteration in the size or texture of the horns. Indeed, the horns of the wild animals would seem to be more prominent than in the domesticated races. The immense horns of the African or Cape buffalo, of the Java buffalo, and the Arnee buffalo of India, are the most valuable, and the extent of the trade

in this class of horns may be estimated from the fact that about one million buffalo horns were shipped from the port of Madras last year. As we derive two-thirds of our foreign supply of horns from the East Indies, it is not improbable that the existing disturbances may cause a deficiency in the shipments thence, owing to the interruption of internal communication, and the withdrawal of large masses of the population from their ordinary peaceful occupation of collecting and bringing in the horns to the mercantile houses. South America (chiefly Brazil and the Argentine Republic) furnishes us with a considerable quantity of ox horns, and we also receive several hundred tons a year from the United States. For buffalo and stag horns we are mainly dependent on India; of the former we import fully 1400 tons per annum. Averaging these at 1400 horns to the ton, this would show a mortality of a million buffaloes a year, besides what may be locally used up, or sent to America and the European ports. Of deer horns, the Sheffield cutlers and others work up about 400 tons, chiefly derived from Ceylon and the peninsula of India. The "fall" from at least 300,000 head of deer is required to supply this quantity. Of the aggregate annual quantity of horns entering the market, estimated at 6400 tons, about one-fifth is manufactured into combs, valued at from 300,000l. to 400,000l.; a large quantity is worked up into knife and cutlass handles; while there are many other miscellaneous uses, in shoe-horns, scoops, drinkinghorns, &c. The waste pieces of stag horn are boiled for size in the cloth-making districts; and the pith or slough of other horns and hoofs is crushed for tillage, when light and thus fit. The heavier portion is converted into prussiate of potash and Prussian blue, of which about 10 tons are made weekly in Sheffield from the waste products.-The Scotsman.

VISIBLE REPRODUCTION OF THE HUMAN VOICE.

M. LEON SCOTT, of Paris, has devised a method for obtaining the Vibrations of the Human Voice expressed in signs, written, so to say, by the voice itself. If we examine the human ear, we find it chiefly composed of a tube ending in the tympanum, an inclined vibrating membrane. It is well known that sound is transmitted with extraordinary purity and rapidity through tubular conduits, and it would appear that, if there were no disturbing causes, the transmission might be continued to an incredible distance without any diminution of intensity. There is an experiment on record, tried about fifty years ago, by M. M. Biot, who, placing himself at one of the extremities of a tubular aqueduct 950 metres in length, carried on a conversation in a low voice with another person situated at the opposite extremity. These facts have been turned to account by M. Scott in the following manner :-A tubular conduit receives the vibrations of the human voice at one of its extremities, shaped like a funnel; at the other extremity there is a vibrating membrane, to which a very light pencil or stylus is attached. This stylus rests upon a slip of paper, covered with a coating of lampblack, and is made by the aid of clockwork to unroll from a cylinder while the