such operation an autopsy of the body should be made and a chemical examination had of its principal organs, so as to ascertain the presence or absence of poison. But these examinations, which have value only when they are conducted in a truly scientific manner, are always delicate, even when the field of investigation has been limited by judicial instructions; and they would become extremely long and troublesome in the absence of any preliminary indication. Moreover, even if it be admitted that they would be conducted with the necessary care and skill so long as the number of cremations is small, it by no means follows that this would be the case when the demands for incineration multiplied.Annales de Chimie et de Physique, V., viii., August, 1876, 571.

THE DIETHEROSCOPE.

Professor Luvini, of Turin, exhibited at the Scientific Loan Exhibition in London, and also at the International Exposition at Philadelphia, an instrument on a totally new principle for measuring atmospheric refraction. Its construction is as follows: If one half of a lens be covered, the image produced by it will differ only in brightness from that formed by the uncovered lens. Moreover, if we take two lenses of unequal focal length, and place them at a distance from each other equal to the sum of their focal lengths, the rays emerg ing from the second will have the same degree of convergence as those entering the first; i. e., the object looked at will appear in its natural size and position. Any agency-such as irregular refraction of the atmosphere-which alters the path of the light from the object to the system of lenses will alter the position of the image formed. If now we have a telescope of such a size that the lenses of the dietheroscope cover half of the aperture of the object-glass, two images of the distant object can be formed-one as seen through the dietheroscope, the other as seen beside it; the latter image being formed by the rays coming directly from the object to the telescope. If the telescope is astronomical the latter image will be reversed, while that transmitted through the dietheroscope will be in its natural position. The distance between these two images will depend upon the refraction of the atmosphere, and so the instrument may be used to measure that refraction. Professor Luvini proposes that four of

his instruments be placed at each observatory, directed to the four cardinal points, and that by their means observations be taken at regular intervals of the condition of atmospheric refraction all around the observatory. He believes that by this method information of coming changes of weather can be obtained earlier than by the means now at the disposal of meteorologists.-18 A, August, 1876, 558.

IMPROVED MODE OF MOUNTING MICROSCOPIC OBJECTS.

Professor Hamilton L. Smith, of Hobart College, New York, has communicated to the Journal of the Microscopical Club a new method of making cells of moderate depth, designed for opaque objects, which is at once simple and easily put in practice. The wall of the cell is made of a brass curtainring. Out of a sheet of dark-green or black wax a disk is punched, a trifle larger than the ring, which is fastened to the centre of the slide by melting. The ring is pressed into this, centred, pressed quite through, and the whole finished with Brunswick black. The object is attached to the wax by previously moistening it with turpentine. The cover is dropped just within the ring, its surface being flush with it, and fastened with the black varnish. The soft and delicate appearance of these wax backgrounds gives an exquisite finish to the slide, the absence of obvious cementing material for the object lending an additional charm. Dr. Smith also uses the sheet wax for cells, cutting rings out of it of any desired color, and attaching these both to the slide and cover by slight fusion. The rings are prepared by means of a specially devised press, consisting of a plunger the size of the hole, a centring and a supporting plate. Disks of the sheet wax are dropped in and the hole made in them, the plunger being wetted to prevent adherence.

CURIOUS JAPANESE COMPASS.

Captain J. H. Murray, of the screw-steamship Scaresbrook, obtained from a Japanese pilot at Yokohama, in 1874, a remarkable compass, a description of which has been given to the public by Buckland. The compass was taken from the wreck of a junk which had been lost on the island of Vries, a volcanic island at the entrance to Yokohama, the smoke of which, with the snow-capped peak of Fusiyama, indicates the

entrance to the harbor. The pilot could give no information about the compass, except that it was found on board the wreck. It is of a circular form, measuring 13.5 inches across, is cast in bronze, and weighs twenty-one pounds. It has a thick rim, in which two ordinary compasses are set, one on each side. The centre of this remarkable plate-like looking object is considerably raised from the surface, and is covered with a number of raised spots or stars of various sizes, each more or less connected by lines with its neighbors. The shapes of these star-like objects are remarkable; in the centre there are five which are larger than the rest. Then there is another group very like a net; another group represents almost a complete circle of these stars; another represents a Y, with the arms closed together; another a Y with the arms extended. Altogether there are no less than two or three hundred of these elevated spots of different sizes. Running throughout the whole series are several lines radiating from a circle drawn around the centre. The brass rim on which the compasses are set is divided into 360 degrees, the same as in an English compass. At every thirty degrees there is a Japanese character. Neither Captain Murray nor any one to whom he has shown this curiosity at home or abroad has any idea whatever of the meaning of the star-like bodies in the centre, or for what purpose the Japanese used them; but it is quite certain that they must have been of some use to them. It is most interesting that these rude characters should be united in the same instrument with the 360 degrees of modern civilization. The casting of the instrument is marvelous.-2 A, 1876.

CLAMOND'S THERMO-ELECTRIC BATTERY.

The latest form of the Clamond battery consists of an alloy of two parts of antimony and one of zinc as the negative metal, and ordinary tinned sheet-iron as the positive element, the current at the heated junction flowing from the iron to the alloy. This alloy is cast in the form of a flat bar, broader in the middle than at the ends, and measuring from two inches to two and three-quarter inches in length, by three eighths to one inch in thickness. The sheet-iron, properly stamped out, is placed in a mould into which the melted alloy is poured; before the alloy has cooled the mould is open

ed and the bars are removed. The alloy melts at 500° Fahr., and expands considerably on cooling. It improves on recasting, but is always very brittle. The bars are arranged radially around a temporary brass cylinder, a thin slip of mica being inserted between the iron and the alloy to prevent contact except at the point of junction. Eight or ten of these bars form a ring, and the several rings are placed one above another, insulated from each other by a circle of asbestus. The inner ends of the bars are heated by a Bunsen burner, the flame issuing in small jets in the annular space between the burner and the bars. The consumption of gas is said to be one cubic foot for each volt of tension per hour. The electromotive force of this combination is such that twenty elements are about equal to one Daniell cell-about one volt. The following table, given on the authority of Latimer Clark, gives the constants of these batteries as sold in London:

When hot, the resistance of the batteries rises about 25 The smallest of the above piles costs about $15, per cent. the largest about $150. A battery of 375 pairs-the internal resistance of which was 4.5 ohms, and the electromotive force 14.6 volts-deposited 180 grains of copper per hour. The electric light which they give is powerful and constant; but it requires a large number of elements.-Telegraphic Journal, 1876.

THE GRAMME LIGHT IN RAILROAD DEPOTS.

Sartiaux has communicated to the French Academy the results of his experiments on the practical use of the electric

light of the Gramme machine in illumination, undertaken at the request of the Compagnie du Nord, their stations being used for the purpose. The machines selected for the trials were those rated at 50, 100, and 150 Carcel burners respectively, equivalent to 350, 700, and 1050 candles. The experiments were made in the baggage-room and in the station itself; the former having an area of about 16,000 square feet and a volume of about 670,000 cubic feet, the latter an area of nearly 120,000, and a volume of 10,500,000 feet. The force used was derived from both steam and gas motors, the power being measured with a Prony brake. The Serrin lamp was employed. The results obtained are tabulated as follows:

As M. Tresca showed, the force necessary to produce a light, say of 700 candles, increases rapidly as the total light diminishes. The light being 12,950, 2100, 1050, 700, and 350 candles, the force required is 0.415, 0.920, 1.7, 2.4, and 4.4 horse-powers respectively per 700 candle-lights. Moreover, it will be observed that a little more force is needed to get the light from carbons nine millimeters square than from those which are seven. Calculating the expense of this light as compared with gas, Sartiaux finds that a gas-light of 700 candles requires a consumption of 15.75 cubic meters of gas per hour, which, at the price of 0.3 franc per cubic meter, would cost 5.7 francs ($1.14). The electric light of the same power requires 2.7 horsepower, which, at 0.09 franc per hour, is 0.24 franc. Add to this 0.09 for the carbons, 0.45 for engineer, 0.20 for interest, etc., the total expense is 0.98 franc (nearly 20 cents); being between a fifth and a sixth of the expense of gas. Moreover, the greater extent of surface illuminated increases this difference exceedingly; since to give the same illumination with gas would certainly require at least twenty-five