There has been much said in recent times about the distribution of electricity by means of induction coils, and the use of this process has given rise to several systems that differ but little from one another in principle.

The following are a few details in regard to a system due to a Dutch engineer:

In the month of December, 1881, a patent relating to the distribution of electricity was taken out in Germany and other countries by Mr. B. Haitzema Enuma, whose system is based upon a series of successive inductions. The primary current developed by a dynamo-electric machine gives rise to secondary, tertiary, etc., currents. The principal line runs through the streets parallel with their axes, and, when the arrangement of the places is adapted thereto, it is closed upon the generator itself. In those frequent cases where it is necessary to cause the line to return over a path that it has already traversed, it is more advantageous to effect the return through the earth or to utilize the street water mains or gas pipes as conductors. This return arrangement may likewise be applied to the lines of secondary, tertiary, etc., order, as may easily be seen.

The induction is effected by the aid of bobbins whose interior consists of a bundle of soft iron. The wire of the inducting current is wound directly around this core. The wire of the induced current is superposed upon the first and presents a large number of spirals. It is useless to say that these wires must be perfectly insulated from each other, as well as from the soft iron core. We shall call primary bobbins those which are interposed in the principal line, and secondary bobbins those in which the inducting current is a secondary one, and so on.

It will be at once seen that this arrangement permits of continuing the distribution of electricity to the interior of buildings by the simple adjunction of one or several bobbins. Each electric apparatus, whether it be a lamp or other mechanism, is furnished with a special current. If the number of these apparatus be increased, it is only necessary to increase the number of bobbins in the same ratio, on condition, be it understood, that the intensity of the currents remain sufficient to secure a proper working of the apparatus in question. When such intensity diminishes to too great a degree, the bobbin must be replaced by a stronger one.

DISTRIBUTION OF ELECTRICITY BY INDUCTION.

It results from what precedes that each apparatus must be put in in such a way as to permit, of the opening and closing of the corresponding circuit. This arrangement, moreover, has no need of being dependent upon the apparatus, and may just as well be transferred to any part of this same circuit. As regards lighting, it is preferable to employ alternating current dynamo machines; yet there is nothing to prevent the use of continuous current ones, provided that there is an arrangement that permits of constantly opening and closing this same circuit. That portion of the line which is placed under ground is insulated in the ordinary way at the places where it is necessary. As for the underground circuit and the induction coils connected therewith, these are protected against all external influence, and are at the same time insulated very economically by covering them with a coat of very fine silicious sand mixed with asphalt.

It is only necessary to inspect the annexed figure to get an accurate idea of this system of distribution. C represents the building in which the generator of electricity, D, is placed; B, the public street, and Q the house of a subscriber. The principal line, E, starts from the terminals, a, b, of the machine, passes through the primary bobbins, G, and is closed through the earth at F. It will be seen that the primary current communicates through d and c with the internal winding of the bobbins, G, while the secondary currents, H, are connected through e and fwith the external winding. The same arrangement is repeated for the tertiary currents, M, and the quaternary ones, o, p. In the annexed example all the lines that run parallel with the axis of the streets are closed through the earth, while those that have a direction perpendicular thereto enter the houses of subscribers and form a closed circuit. In the interior of these houses the wires, as well as the induction coils, are insulated and applied to the walls.

At Q is represented the arrangement that would have to be adopted in the case of a structure consisting of a vestibule, r, and two rooms, s, lighted by two electric lamps, R. In the portion of the figure situated to the left it is easy to see the process employed for insulating the line. A commencement is made by digging a ditch in the street and paving the bottom of it with bricks. Upon these latter there is laid a mixture of sand and asphalt, and then the wires and bobbins are put in, and the whole is finally covered with a new insulating layer.

It is a simple statement that we make here, and it is therefore not for us to discuss the advantages and disadvantages of the system. If we are to believe Mr. Enuma, the advantages are very numerous, to wit: (1) The cables have no need of being of large size; (2) the intensity is the same through the entire extent of the primary circuit, secondary one, etc.; (3) the resistance is invariable in all portions of the line; (4) the apparatus are independent of each other, and consequently there may be a disturbance in one or several of them without the others suffering therefrom; (5) either a strong or weak luminous intensity may be produced, since, that depends only upon the size of the coil employed; (6) there is no style of lamp that may not be used, since each lamp is mounted upon a special circuit; (7) any number of lamps may be lighted or extinguished without the others being influenced thereby; (8) when a fire or other accident happens in a house, it in no wise interferes with the service in the rest of the line; (9) the system could, were it required, be connected with any other kind of existing line; and (10) the cost of installation is infinitely less than that of a system of gas pipes embracing the same extent of ground. - La Lumiere Electrique.