d wire contact which secures the ideally
perfect "nibbing points," and he makes these wires of dissimilar
non-corrosive metals (gold and platinum).

He replaced previous rule-of-thumb methods by scientific calculation,
recognized the value of low voltage, good insulation and the avoidance
of self-induction, with the result that the electro-pneumatic action
has become (when properly made) as reliable as the tracker or pneumatic
lever mechanism.

DESCRIPTION OF THE ELECTRIC ACTION.

The electric action consists substantially of a small bellows like the
pneumatic lever, but instead of the valve admitting the wind to operate
it being moved by a tracker leading from the key, it is opened by an
electro-magnet, energized by a contact in the keyboard and connected
therewith by a wire which, of course, may be of any desired length. We
illustrate one form of action invented and used by Hope-Jones.[5]

Within the organ, the wires from the other end of the cable are
attached to small magnets specially wound so that no spark results when
the electric contact at the key is broken. This magnet attracts a thin
disc of iron about 1/4 inch in diameter, (held up by a high wind
pressure from underneath) and draws it downward through a space of less
than 1/100 of an inch.

The working is as follows: The box A is connected with the organ
bellows and so (immediately the wind is put into the organ) is filled
with air under pressure, which passes upwards between the poles of the
magnet N. Lifting the small iron disc L it finds its way through the
passage L into the small motor M, thus allowing the movable portion of
the motor M to remain in its lower position, the pallet C|1| being
closed and the pallet C|2| being open. Under these conditions, the
large motor B collapses and the pull-down P (which is connected with
the organ pallet) rises.

[Illustration: Fig. 6. The Electro-Pneumatic Lever]

When a weak current of electricity is caused to circulate round the
coils of the electro-magnet N, the small armature disc J is drawn off
the valve-seat H on to the zinc plate K.

The compressed air from within the small motor M escapes by way of the
passage L, through the openings in the valve seat H into the
atmosphere. The compressed air in the box A then acts upon the movable
portion of the small motor M in such a manner that it is forced upwards
and caused (through the medium of the pull-wire E) to lift the supply
pallet C|1| and