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sparks, not only by their form, their light, and their noise, but also by other peculiarities, such that a further investigation into their nature has been made by him. Among the isolated points considered in connection with these feeble sparks, Riess states that Wiedemann and Ruhlmann have from special investigations concluded that the quantity of electricity necessary for a discharge is much greater when the discharge takes place from the negative than from the positive electrode. But his own experiments seem to him not to justify so positive an expression, as they can be explained by means of the feeble glimmer that precedes an eruptive discharge. We have, moreover, no experiments which would lead us to think that there is a greater quantity of electricity present in a positive than in a negative spark. From experiments made with the Holtz machine, he concludes that the greater length of the negative electrode is not an important condition in producing feeble sparks, but that in these experiments electrodes may be employed of any length whatever. The feeble sparks are, not only in reference to their length, but also to their light and brightness, independent of the composition of the arms of the discharger by means of which they take place. - Mo. natsbericht der Berlin Akad., 1875, 152.

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TELEGRAPHIC GROUND CURRENTS. Speaking of the importance of observing the underground or so-called earth currents on electric telegraph wires, Sir William Thomson states that an observation which would be of value for scientific study is to observe the indication of the electrometer at each end of the telegraph line at any time--whether during a magnetic storm or not-during the day or night. If the line be worked with a condenser at each end, this observation can be made without in the slightest degree disturbing the practical work through the line by simply putting on an electrometer in direct connection with the line, and connecting the outside of the electrometer with a proper earth connection, when it may be observed, quite irrespectively of the signaling, when signaling is done, as it very frequently is, on submarine lines with a condenser at each end. The scientific observation will bo disturbed undoubtedly by the sending of messages; but the disturbance is only transient, and in every pause at the end of a word there will be a sufficiently near approach to steadiness in the potential at the end of the wire connected with the electrometer to allow a careful observer to estimate with practical accuracy the indication that he would hav were there no work of the line going on at the time. A magnetic storm of considerable intensity does not stop the work--does, indeed, scarcely interfere with the work of a submarine line in many instances—when the condenser is used at each end. Thus observations, even when the line is working, may be made during magnetic storms, and again during hours when the line is not working. Any single observation, or any series of observations, that are made on the electric potentials at one end of the insulated line will give valuable results. When an arrangement can be made for simultaneous observations of the potentials of the electrometer at the two ends of the line, the results will be still more valuable. We may substitute, with satisfactory results, for the electrometer, the galvanometer of very large resistance. --Jour. of the Soc. of Telegraph Engineers, III., 1874, 10.

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THE ELECTRICAL VOTING MACHINE. Monsieur J. Morin has presented for inspection a model voting machine constructed for a deliberative body of twelve voters, in which he proposes to simplify, in a considerable degree, the tedious process of voting, and to economize the time of an assembly. To attain this end the machine ought to be prompt and certain, and free from errors as to the result of the votes. It is composed of a portable table, having twelve circular openings, below which are written the names of the members, each opening corresponding, by invisible wires, to the place of the representative named upon the table. Beneath are placed two small openings closed by small covers, which disappear at the end of the operation, so as to allow one to see the number of votes that have been cast for and against the project. Each of the deputies has also two balls, black and white, corresponding to the opening which belongs to him in the table. The operation of the process is as follows: The deputy, by touching a button, draws before the opening placed upon the table and under his name a disk of the same color as the ballot that he wishes to throw, and which closes the opening. By the interior arrangement of the machine, a vote being once made prevents the expression of a second, so that it is impossible to vote twice. When the president is sure that every one has taken part in the vote, he touches a special button placed at the side of the machine, and instantaneously the work of addition begins. In this operation, by an ingenious contrivance, the white balls are separated from the black, and the totals thus formed occupy two appropriate places upon the table. At this moment the little covers remove themselves, and allow one to see the figures resulting from the addition. At the moment when the president sets the process of addition into operation, all voting is suspended, so as not to de. range the work. Upon the back of the machine there is a system of needles corresponding to each of the openings, which, as soon as the vote is terminated, prints the result upon a sheet of paper prepared for this. A lateral lever permits the reinstating of every thing in its initial condition, ready for a new operation. All these operations are performed by electricity and instantaneously, and the author says that one minute will suffice to count the votes of an assemblage of seven hundred and fifty persons. The complete machine is now manufactured to order in Paris, the cost being about twenty dollars per voter. -- 1 B., 1875, 206.

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THE THEORY OF THE ELECTRICAL MACHINE. Poggendorff states that few problems in physics have as yet defied all theories so completely as those offered by the electric machines. Theories there are in plenty; but none explain all the facts, and none are free from unwarranted assumptions. He himself inclines to the opinion that it will not do to assume that the particles of electricity are spherical, and exert their action equally in all directions; but that it is more likely that they are polarized; that they have a definite range on the electrified surface; and that in consequence of the movement of this surface the particles themselves turn. The development of this idea, which is in opposition to the assumption of two electric fluids, as commonly held in Germany, seems, however, to him to be attended

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with insuperable difficulties. He appears to have been led
to this suggestion by observing the effects produced by turn-
ing the revolving plate of an electric machine of the second
class through measured angles of 45°, 90°, 135°, etc., instead
of turning it steadily throughout the entire circumference.-
Berlin Akad. Monatsb.

THE ELECTRIC CONDUCTIVITY OF LIGNEOUS SUBSTANCES.

Count Du Moncel has investigated the question as to whether the conductivity of wood fibre, if electrified, is due to the humidity with which bodies are more or less impreg. nated. His experiments, being conducted with extremely sensitive apparatus, have led him to the following conclusions: A small frame of oak, regarded by the cabinet-maker as being very dry, furnished, when it was brought to him, a deflection of 55° of the scale of the galvanometer. This same small frame, when it had been dried for two hours in the stove, gave not the least deflection, and being kept in a sunny chamber for several hours did not increase its conductivity. Exposed to the air during a dry July night, it gave in the morning a deflection of 13°. It appears from his experiments that it is to the humidity aspired through its pores that the wood owes its relative conductivity, and that this conductivity is proportionate to the degree of pressure upon the metallic plates by means of which the electric current is communicated to the block of wood.Proc. Soc. Teleg. Engineers.

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CIRCULAR MAGNETIC NEEDLES.
A report has been presented by Duchemin on the experi-
ments made on board of the French vessels Faone and Savoie,
upon the properties of magnetic needles made in the form of
a circular disk, instead of a pointed or lozenge-shaped one.
Two series of experiments were made: first, with reference
to the comparative steadiness of the simple and the circular
needles; second, with reference to the correction of the circu-
lar needle for local influences by the addition of a concentric
movable circular magnet. The sensibility of the circular
needle, according to him, leaves nothing to be desired, being
superior to that of the ordinary compass, although its friction
is greater, since its weight is more than twice as great. The

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stability of the circular needle, as shown by its oscillations to the right and left, is greater than that of the ordinary needle; and its moment of inertia is, in fact, equal in all positions. No difficulty is experienced in locating the position of the magnetic axis of the circular needle. These needles are magnetized instantaneously by means of a powerful softiron electro-magnet. He concludes that the circular compass-needle is an instrument worthy of navigators; and by perfecting its construction we shall come into possession of a simple, sensitive, stable instrument, constituting a veritable improvement on the present arrangement. It is even stated that the extreme sensibility that can be given to this instrument may render it advantageous in magnetic observations. A portion of the errors of the instrument, due to local attractions, may be corrected by means of a circular magnet; but this is not to be recommended, as new complications are thereby introduced.-Bull. Hebd. Assoc. Scientifique.

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CORRECTIONS OF THE COMPASS ON IRON SHIPS. From an elaborate memoir, by Garbich, on the theory and practice of the deviation in compasses on iron ships, we take the following directions for effecting the compensation of the compasses. In order to avoid the employment of large masses of iron, it is best to use two iron rods placed diametrically opposite to each other. To determine exactly the distance of these rods from the centre of the compass, it is best to turn the ship's head toward that point in the horizon at which the quadrantal deviation is a maximum, after first allowing for the semicircular deviation; then, by moving the rods to or from the centre of the compass, to annul the maximum quadrantal deviation. This error being thus compensated, it will be found that a portion of the rolling or heeling deviation is also removed. The semicircular deviation is then best compensated, by means of two magnets, as follows: Under the centre of the compass is fastened a non-magnetic metallic parallelopipedon of square section, one side of which is parallel to the keel; the lower side of this should be fastened to a metallic disk of the same material, and this so fastened by screws to the base of the binnacle that its position can not be altered with reference to the keel of the vessel. On the upper end of this parallelopipe

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