This machine, however, as before stated, has never as yet been constructed, so that experimental data relative to its mode of working are wanting. It is especially interesting as regards its origin, which dates back to an epoch at which researches on the dynamo electric machine were at their heat. It is in its historical aspect that it is proper to regard it, and it is from such a point of view that we have deemed it well to say a few words about it in this place.—La Lumiere Electrique.
Zeitschrift des Electrotechnischen Vereines in Wien, July, 1883.
BORNHARDT'S ELECTRIC MACHINE FOR BLASTING IN MINES.
We shall not attempt to pass in review the several apparatus that have hitherto been devised for igniting blasts in mining operations, but shall simply describe in this place a machine recently invented for this purpose by Mr. Bornhardt, an engineer to the Grand Duke of Brunswick.
This apparatus (shown in the accompanying engravings) consists essentially of two hard-rubber disks, A (Figs. 2 and 3), keyed to an iron axle, and of two rubbers, B, that are formed of skin and are held against the disks by small springs, R; motion is communicated to the axle, a, by means of a pair of gearings, a and b, and a crank, f.
Each disk revolves between two metallic rings, c, provided with points that attract and collect in Leyden jars, D, the electricity produced by the friction. For discharging the condensers there is employed a manipulator formed of a rod, mm, which can be acted upon, from the exterior, by means of a button, k. Upon bringing the ball, m, of the rod in contact with the ball, p, of the condenser, the lever (which then takes the position shown by the dotted line) continues to remain in connection with a small ring, q, through a special spring. Another ring, t, is connected in the same way with the external armature of the condenser. Upon connecting the rings, p and t, by a wire to which cartridges are attached, any number of the latter may be ignited.
The parts that we have just enumerated are inclosed in a tin box covered with a wooden casing, P. Between the two there is inserted a sheet of hard rubber in order to prevent a loss of electricity; the whole is held in place by strong springs.