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electric light in increasing the brightness of the arc. The substances used were bone-ash, calcium chloride, borate and silicate, silica, magnesia, magnesium borate and phosphate, alumina, and aluminum silicate. The proportions were so regulated that, when burned, the carbons should contain about five per cent. of the foreign substance. The results show that only with the bone-ash was the light increased measurably, but that the fumes produced are serious objections to the use even of this.

Reynier has suggested a new form of electric lamp, the carbons in which have the form of disks, in contact, or nearly so, at their peripheries, and rotated by clock-work. To one of them an automatic arrangement is attached, which electro-magnetically controls the distance between the electrodes, and that instantaneously. This device, the author believes, will enable him to divide the current, and so to maintain several electric lights at the same time by a single machine.

Chikolef has made a series of experiments at St. Petersburg to determine the lighting power of the electric light at great distances. The power of the light is notably increased by covering the carbon of the lamp with a thin sheet of copper (one sixteenth of the diameter of the carbon at its upper part, and from one forty-eighth to one sixty-fourth in its lower part). It depends also upon the direction given to the carbon, the best being to turn the cup towards the object to be lighted. The great machine of Alteneck, with a carbon twelve millimeters in diameter, gave a maximum light equal to 10,210 candles, and a mean light of 5739 candles; while with a carbon of ten millimeters, but galvanically coated, it gave a maximum of 16,255 candles (20,275 when the cup is turned as above), and a mean of 14,039 candles. The light was sufficient to make objects visible (for military purposes) at a distance of 3080 yards. Of many machines used, the most economical proved to be the great Alteneck.

Jablochkoff has devised a new form of electric lamp, very simple in its construction, having absolutely none of the mechanical arrangements ordinarily used. It consists of two carbons permanently fastened parallel to each other, and at a small distance apart, separated by some insulating sub

stance capable of disappearing in some way as the carbons burn, the substance used by the discoverer being either kaolin or a mixture of sand and powdered glass. To prevent the more rapid consumption of the positive carbon, it is made of proportionately greater cross section, the author having found that the relative rapidity of consumption depends on the strength of the current. The light is double that given by a regulator, and with an ordinary Gramme machine current four lights were produced at the same time.

Experiments have been made in both London and Paris with the electric candle of Jablochkoff, using two carbon strips placed side by side, insulated from each other by some non-conducting substance which melts or volatilizes as the carbons burn. At the West India Docks in London four of these candles were simultaneously burned with the current from one magneto - electric machine. The large yard was brilliantly illuminated, although the candles were enclosed in ground-glass shades; so that it was possible to read small print at a considerable distance, while at the same time the eyes were not affected by the glare, as is the case with the ordinary electric light. The second trial was the lighting of the top story of one of the large warehouses, and the third the lighting-up of a large vessel at the quay, both of which were successful. Each candle gave a light equal to that from 100 gas-lights, and at a very much less cost.

Another form of Jablochkoff's light has been variously tried, which seems likely to be of more practical use than the candle. It consists of a thin kaolin plate, only four millimeters thick, but eight centimeters long and two or three wide, having the conducting wires fastened in grooves at the ends. These wires are coarse, and come from the secondary coil of an inductorium, the primary coil being in the circuit of an Alliance magneto-electric machine, driven by a three-horse engine. When the secondary current crosses the kaolin plate it apparently ignites, giving a soft mellow light equal to that from eight gas-burners. In the Paris experiments three electric candles, each equal to five kaolin lights, were operated in the main circuit, while ten of the kaolin lights were operated by as many secondary circuits, thus making it possible to feed twenty-five lights at once in

different places by the same machine. These experiments were made with a view to utilize these lights at the Paris Exhibition.

Tyndall, in connection with Douglass, bas made a report to Trinity House on the comparative value of various magneto-electric machines for light-house purposes, an abstract of which appears in Nature for October 25th. The machines compared were those of Holmes, Gramme, and Siemens. The performance of the small Siemens machine particularly impressed them. Its power, in relation to its size, is surprising. The large machine of Siemens, however, greatly transcends both his small machine and the single machine of Gramme; it is sensibly equal to the two Gramme's machines coupled together, the price of the former being less than half that of the latter. The light from the large Siemens, as also that from the two coupled Grammes, is of extraordinary splendor. Combining either the large machine of Siemens, the two Gramme's machines, or, if practicable, the two small machines of Siemens, with one of the group-flashing dioptric apparatuses which have been recently devised by Dr. Hopkinson, a light transcending all other lights now existing would probably be obtained.

7. Thermo-Electricity. Streintz has described a new form of Noë's thermo battery, and has given the results of some measurements with it. The positive metal consists of an alloy of 62.5 antimony and 36.5 zinc, and the negative metal of German-silver wire. The battery contained four series of 27 elements each, so arranged as to be combined in two series or in one only. The electro-motive force estimated by Fechner's method was that of 4.3 Daniell cells; the resistance, 2.7 Siemens units.

Naccari and Bellati have investigated the thermo-electric properties of potassium and of sodium at various temperatures, using pairs formed by one of these metals and copper in the earlier experiments, and lead in the later. The results show that the passage of a unit of electricity from a cold section to another warmer by one degree, transports, following the direction of propagation of the negative fluid, a quantity of heat equivalent respectively to 2529 units of work for the potassium and 4129 units for the sodium, The neutral points are at - 62.04° and -212,4°,

CHEMISTRY.

By GEORGE F. BARKER,
PROFESSOR OF PHYSIOS IN THE UNIVERSITY OF PENNSYLVANIA, PUILADELPHIA.

. GENERAL. Among the interesting Chemical papers of the year we note one by Berthelot on certain chemical phenomena produced by the electricity of tension. In these experiments a Holtz machine was employed, one electrode of which was connected by means of a platinum wire with the internal coating of a sealed tube containing the substance to be acted on, the external coating being connected with the internal one of the next tube, and so on, the second electrode of the machine being put in communication with the last outer coating. No spark can possibly occur within the tubes, though they are incessantly charged and discharged, but always with the same kind of electricity. He finds that ozone is formed from oxygen equally well by positive or negative charges, though the amount produced is increased with the tension, being five or six per cent. for sparks one centimeter long, while with sparks of half a millimeter only one or two thousandths is formed. No production of nitrous compounds was observed with a mixture of nitrogen and oxygen. Acetylene was formed in quantity when organic vapors were placed in the tubes. Nitrogen was freely absorbed by organic bodies such as paper and dextrin. Experiments are in progress to determine the cause of the special action thus exerted.

Terreil has published an extended paper on Dulong and Petit's law of atomic heats, in which he compares together the products of specific heat and atomic weight of bodies in the state of vapor, and finds a close accordance with the law. He asserts that a body not gaseous has a specific heat twice that which the same substance possesses in the gaseous condition.

Victor Meyer has described an improved form of appara

tus for showing the increase of weight in combustion where the products are gaseous. Upon each scale pan of a balance is placed a candle. Above it is a glass gas chimney, having gauze at bottom, and containing several large pieces of caustic soda, suspended to the stirrup. One of the candles being lighted, in a very few minutes that side of the balance preponderates. In six minutes there is a difference of weight of a gram, and in fifteen minutes of more than three grams.

A lecture was delivered in March before the London Chemical Society, by T. E. Thorpe, on the theory of the Bunsen lamp, in which he gives first a bit of history relative to its origin, and then discusses the results of Mallard as to the velocity of inflammation in meters per second of various mixtures of coal-gas and air, of Blochmann on the composition of the gas at various parts of the flame, and of Heumann and Frankland on the cause of the disappearance of luminosity in the flame.

Müller has proposed a simple apparatus for determining approximately the density of gases, as a lecture experiment. A well-closed half-liter flask, through the cork of which passes a glass tube drawn out to a point, is taken, and water is boiled in it until all the air is expelled from its interior, when the point is sealed. After cooling it is carefully weighed. The difference is the weight of the contained air, corrections being made for the tension of aqueous vapor and for temperature. Replacing the stopper by a second having two tubes, and again expelling the air from the flask, it is successively filled from a gasometer with the gases to be weighed, and their weights determined in succession. The method is quite accurate.

NON-METALLIC. Schobig, at Kämmerer's suggestion, has experimented to determine the effectiveness of a solution of potassium permanganate for the purification of hydrogen gas for analytical uses. He finds it highly satisfactory, the impurities present-sulphur, arsenic, antimony, phosphorus, and carbonall being completely removed. The hydrogen itself is oxidized by the solution, but only to a slight extent. The hydrogen thus purified the author finds will reduce silver.

Corne has observed that if to an aqueous solution of an iodate there be added a few drops of water in which phos

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