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._

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