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of the roof, and especially to the rain-water pipes, in order that greater facility may be offered to the electric fluid in its passage to the earth. — American Engineer, I., 122.

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ATMOSPHERIC ELECTRICITY IN SPITZBERGEN. In reference to the observations of atmospheric electricity in high northern latitudes, in which, as yet, our instruments have generally given negative results, Wijkander states that the late Swedish polar expedition gave special attention to this subject, and that all their observations show that at relatively high temperatures the air conducts electricity very well, to which fact is ascribed the absence of lightning and the presence of the Northern Lights. It has been said that these latter phenomena depend upon the great moisture of the air in these regions; but it seems clear that the polar light is conditioned by other circumstances, since the same temperature and the same degree of humidity do not bring forth these results in other latitudes.--19 C, VII., 422.

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VELOCITY OF TIIE TRANSMISSION OF ELECTRIC FORCE. The question as to whether electric and magnetic forces require sensible time to exert their influence, at a distance, has been made the subject of numerous investigations, one of the most interesting of which is that of Herwig, who has endeavored to conduct experiments upon as large a scale as possible. The preliminary results to which he was led have, he thinks, justified him in formulating the conclusion that if the terrestrial magnetic influence has any definite velocity of transmission whatever, it must be at least at the rate of half a million of miles per second; and that the influence of the earth's magnetism at any point of the earth's surface attains its full degree within ju of a second. -19 C, VIII., 30.

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EDLUND'S THEORY OF THE NATURE OF ELECTRICITY. In a report on the theory lately advanced by Professor Edlund as to the nature of electricity, Dr. Emsmann states that apparently Edlund has, in this matter, taken such a step forward as was made when previous investigators were able, by means of one æther, to explain both optical and thermal phenomena. Edlund's theory consists essentially in ascribing to the æther itself an inertia which necessitates a slight interval of time in order to affect its movement. The flow of æther from one body to another explains the electro-dynamic phenomena, while its abundance or deficiency in any body serves to explain the electro-static phenomena. As regards the chemical influence of the galvanic current, it is assumed that the electricity has an equal influence upon the bodies that are to be separated or combined by it. The rotation of the plane of polarization of light is elucidated by the simple assumption that the electric æther is not different from the optical æther, and it must be acknowledged that Edlund's thcory is based upon well-known facts, and is distinguished by its simplicity and sufficiency.--7 C, X., 402.

ON THE ELECTRICITY OF MINERAL WATERS,

Professor Theury, of Geneva, and Dr. Minnich have conducted some remarkable experiments in reference to the electrified condition of the mineral waters of certain springs, respecting one of which, the Stadthof, near Baden, in Switzerland, they state that their experiments show that the warm water at its escape from the soil is quite strongly electrified, it being negatively electrified with reference to the electric current at the thermal spring at Limmat. The currents observed by them are not the result of any

thermo-electric action, nor are they the result of any special electric chemical action between the carbonic acid gas and the platinum electrode, but appear to them to be peculiar to the springwater itself.---13 B, III., 186. TUIE STRATIFICATION OF ELECTRIC DISCHARGES IN VACUO.

Messrs. De la Rne, Miller, and Spottiswoode have conducted a long series of investigations looking to the ascertainment of the cause of the stratification of electrical discharges in vacuo. Without bringing their investigations to a close, or pointing out any conclusions as distinctly reached, it is evident from their experiments that the stratification is due to a peculiarity in the flow of the electricity, which flow is apparently of the nature of an intermittent discharge, whose periodical overflows, so to speak, take place at very short intervals, and whenever the current acquires strength enough to overcome the resistance offered by the rarefied medium through which it must flow.

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EARTII-CURRENTS ON TELEGRAPHIC LINES. The Asiatic Society of Bengal, in consideration of the important labors of Mr. Schwendler, has taken steps to influence the government of India to especially investigate the subject of earth-currents on telegraph lines—a work which ought, in the interest both of science and art, to be taken up not only by the European governmental, but by American private telegraph companies.

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ON UNILATERAL CONDUCTIVITY OF ELECTRICITY. While engaged in other work, Dr. Schuster states that he met with an irregularity which seemed to be of such a peculiar nature that he subjected it to a separate investigation; although he is not yet able to raise this phenomenon above the rank of an irregularity, yet his experiments leave no doubt as to the fact. It seems to him clear that the current produced by an electro-motive force in a circuit composed entirely of copper wires, joined together by means of binding screens, may under certain circumstances be different froin the current produced by the same electro-motive force acting in an opposite direction. He calls this phenomenon “Unilateral Conductivity.” The most plausible explanation seems to him to be that a thin layer of air may sometimes intervene between the two wires that are screwed together, an explanation that has been confirmed by some experiments, while others show that it is insufficient.—7 A, XLVIII., 246.

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THE ELECTRIC CHARGE OF A CONDUCTING WIRE. The researches of various physicists have proved that an electric current, before it can circulate in any conductor, must charge it electrically, and consequently in the entrance of a current into the circuit two periods are distinguished. In the first the wire is charged, the current passing through a variable state until it gradually acquires its normal value. In the second period the current has become constant, and its value depends on the conditions determined by Ohm's law. According to Villari, the first or variable state has no constant duration; it increases with the length and condition

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of the circuit, and also with the so-called co-efficient of charge of the wire, which co-efficient is measured by the quantity of electricity necessary to give a unit's charge to a unit's length of wire. This co-efficient of charge varies with every metal, and with it varies the duration of the current's variable state; the quantity of electricity which the current consumes to establish itself is with the different metals also variable.—18 A, XX., 4.

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THE ACTION OF ELECTRICITY ON PHOSPHORUS. In 1860 Dr. Giessler endeavored to show that electricity of itself can effect the conversion of ordinary phosphorus into amorphous phosphorus. An apparatus recently devised by Schwendler shows that the conversion of the phosphorus is effected even by the inducing action of the current of electricity. For this purpose the ends of two conducting wires are inserted into exhausted spheres in which there is no phosphorus. These spheres are inclosed in others, and the space between (likewise exhausted of air) contains the phosphorus, which is therefore completely shut off from the conducting wires by a screen of glass. On the passage of a current the sides of the spheres become coated with amorphous phosphorus. It may be considered demonstrated that this conversion is effected neither by the light nor by the heat that accompany the current, but exclusively by the electricity itself.

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TIIE DIFFERENCES BETWEEN VOLTAIC AND FRICTIONAL

ELECTRICITIES, In reference to the difference between clectricity developed by friction and that developed in the galvanic battery, it has long been remarked that the former, or electricity of high tension, as it is called, excels the other in the development of light by the electric spark, and has a stronger physiological effect upon the nerves and muscles, while its chemical, thermic, and electro-magnetic effects are much weaker. A further difference between these two sources of electricity consists in this, that the galvanic current follows the law of Ohm, varying its intensity with the resistance between its poles, while the current from the electric machine, as was shown by Gauss, remains constant, no matter how great the

resistance of the bodies penetrated by it. The study of the failure of Ohm's formula in this case has been the subject of an investigation by Rossetti, who, among many other conclusions, establishes the following principles : In one and the same series of experiments, conducted under identical circumstances with reference to atmospheric humidity, the intensity of the current excited by the electric machine is nearly, but not exactly, proportional to the velocity of the revolving disk. The relation between the velocity of the disk and the intensity of the current is not independent of the moisture in the air, but varies sensibly therewith, the number of turns the disk must make in a second, in order that a current of constant intensity may be developed, is greater on moist than on dry days. The work required to make the electric machine active is exactly proportional to the intensity of the current, assuming that the humidity remains the same. The ratio between the work and the intensity of the current diminishes with increasing moisture, so that in order, on a moist day, to obtain a current of given intensity, there may indeed be required a greater velocity of rotation; but equally is it true that a less amount of work would be expended, so that the electric machine is more economical on moist days than on dry.-19 C, VIII., 140.

NEW MODIFICATION OF THE LECLANCHÉ BATTERY. M. Kern, of St. Petersburg, after detailing several grave objectionable qualities of the Leclanché cell, at present very popular for telegraphic and other uses, recommends the following modification, which he claims will act very constantly. Two parts of well-washed coke and one of manganese dioxide, in the state of powder, are well mixed together with a small quantity of water acidulated with some drops of nitric acid, and the mixture is then pressed into a cylindrical mould of suitable size. The resulting coke-manganese cylinders are dried in a warm place, but not over a fire, as a strong heat will decompose the peroxide. The dried cylinders are placed in glass jars containing concentrated solution of ammonium chloride, and surrounded with zinc plates curved in the usual manner.

By this arrangement the use of porous cells is avoided, and a battery of such elements acts more constantly, besides which the construction is materially cheap

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