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. In order to show the normal state of the condenser, a scale consisting of 15 metallic buttons to give the dimensions of the sparks, is arranged at X. This scale is capable of being connected with the rings, _q_ and _t_, by means of chains; when the spark obtained after 15 or 20 revolutions considerably exceeds the intervals of the scale, it is a sure thing that the machine is in a proper state. In order to prepare the apparatus for carriage, the winch is taken off and placed in the compartment, _m_, which is closed by means of a door, Q. Figs. 5 and 6 show the arrangement of the dynamite cartridges and wires in the blast hole. Figs. 7 to 10 show different arrangements of the igniting wires. Figs. 11 and 12 give the general arrangement for igniting a number of cartridges simultaneously by means of the electric machine. Fig. 13 shows the arrangement where powder is employed. Fig. 14 shows the arrangement of a horizontal hole.--_Annales Industrielles._ * * * * * IMPROVED ELECTRIC FIRE ALARM.