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ed and the bars are removed. The alloy melts at 500° Fahr.,
and expands considerably on cooling. It improves on re-
casting, 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 pre-
vent 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 Bun-
sen 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:

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120
150
240
380
680
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100
200
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When hot, the resistance of the batteries rises about 25

The smallest of the above piles costs about $15, 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.

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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:

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10.090 meter. Consumption carbon, 7 mm...

0.13 meter,

0.045 of carbon and

neg. pole, waste........ carbon, 9 mm...

0.060 Į pos. pole,

0.09 neg. pole,

0.030 Distance at which reading was easy.... 25 meters. 40 to 45 mtrs. 45 to 59 mtrs.

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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 additional burners. To avoid the glare, the light was inclosed in a globe of ground glass. — Revue Industrielle, VII., May, 1876, 169.

MAGNETISM OF COBALT AND NICKEL. It has long been known that a bar of iron when magnetized becomes appreciably elongated. Barrett has recently sought to discover whether cobalt and nickel are similarly affected. With cobalt, a slight lengthening may be perceived; but in the case of nickel a contraction, abont equal to the expansion of iron, takes place. The bar of nickel used was about two feet long.-1 A, June 30.

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D. CHEMISTRY AND METALLURGY.

CHEMICAL ACTION OF SOLAR RAYS.

Henry E. Roscoe states that although his method of measuring the varying intensity of the chemically active rays as affecting chloride of silver paper has been the means of pointing out many important facts, yet it has not been introduced as a regular portion of the work of meteorological observatories; until which is done we can not hope to obtain any thing like a complete knowledge of the laws of distribution of the chemical rays over the earth's surface. This neglect of Roscoe's method is, in part at least, due to the labor of observing. He has, therefore, advised a modification of the instrument described by him in 1865, and as thus modified the constant sensitive paper is exposed to the action of total daylight at given intervals, say at every hour during the day, by a self-acting arrangement for accurately noting the times. These hourly records are then read off in the evening by the observer. Many mechanical difficulties have been overcome through the skill of Mr. Jordan, of Manchester, and the instruments, as described by Roscoe in the last volume of the “Transactions of the Royal Society of London,” are said to give complete satisfaction. In order to read off the intensities of recorded photographic images, a standard series of graduated tints is provided. Special directions are given for the preparation of the sensitive paper. The correction due to the reflection and absorption of the glass cover is also investigated; and the comparison of observations made by hand, and by the self-recording instrument, over twenty days with the two meth ly agree.-Philosophical Transactions, London, 1875, 655.

OCCLUDED HYDROGEN IN SO-CALLED EXPLOSIVE ANTIMONY. The presence

of a considerable amount of chloride of antimony was demonstrated several years ago, by Professor Böttger, in the so-called explosive antimony formed on the negative pole, consisting of fine platinum wires, the positive one being of massive antimony, when the current of a single additional burners. To avoid the glare, the light was inclosed in a globe of ground glass.--Revue Industrielle, VII., May, 1876, 169.

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MAGNETISM OF COBALT AND NICKEL. It has long been known that a bar of iron when magnetized becomes appreciably elongated. Barrett has recently sought to discover whether cobalt and nickel are similarly affected. With cobalt, a slight lengthening may be perceived; but in the case of nickel a contraction, abont equal to the expansion of iron, takes place. The bar of nickel used was about two feet long.--1A, June 30.

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