or sliding, motion only. This remarkable machine is illustrated in Fig. 80. The magnets consist of tungsten steel permanently magnetized and fastened to cast-iron pole pieces which carry the magnetic lines of force from the poles to the soft iron cores. The pole pieces are fastened to the base casting and support the magnets'

cores and coils. The cores fit into slots in the pole pieces and are built up of sheets of soft iron, and each core extends from just beneath the upper armature down through a pole piece and coil to just above the bottom armature. The armatures consist of sheets of soft iron mounted on a spool-shaped piece which in turn is loosely fitted onto the squared end of the armature bar. This armature bar is

a piece of steel, its central cross-section being flat while its ends carry the armatures and are square. This leaves shoulders which bear against the armatures through the medium of fibre washers, the shoulders serving to carry the armatures in and out of contact with the cores when in operation. The armature itself is freely supported by a box-shaped guide which is fastened to the case. On the outer ends of the armature bar are spiral springs held in place by cup-shaped washers and pins, making a self-locking fastening similar to valve-spring fastenings. These springs bear against the armatures and force them against the shoulders of the armature bars. The coils each have a simple, hightension winding and are connected by a metal strip, thus making a continuous winding. In the singlecylinder machine one end of the winding is grounded to the case of the igniter while the other end runs to the spark plug of the motor. In two-cylinder machines no ground connection is used, but both ends of the windings are connected to the plugs of the motor. In the back of the case there is a square slot in which slides the square driving bar. This bar receives its motion. from the engine and at its upper end is provided with a pivoted latch of hardened steel. The latch is held in against the latch block by a spring which fits into a recess between the latch and the driving bar. Above the latch is a hardened steel timing wedge which is held upward against the timing quadrant by a spiral spring. The timing quadrant is pivoted on the back of the case and is moved by a small handle projecting above the

case.

As the driving bar, connected with the engine, is moved upward carrying the latch with it, the shoulder on the side of the latch snaps under the square head of the latch block. As the motion reverses, the latch carries the latch block and armature bar upward. The lower armature being in contact with the stationary cores cannot rise with the bar, but the lower spring is compressed between the retaining washer and the armature while the bar rises and carries with it the upper armature which bears against the upper shoulders on the bar. As the driving bar continues its upward motion the bevelled upper end of the latch meets the lower end of the timing wedge, and as the wedge is stationary a further movement of the latch causes it to be pushed aside until its shoulder clears the latch block and releases it. As the lower armature spring is at this time. exerting a pressure between the armature bar and the cores through the lower armature, the instant the latch is released the armature bar is pulled quickly downward carrying the upper armature with it. Just before the motion of the upper armature is stopped by hitting the cores, the lower shoulders on the armature bar come in contact with the lower armature and its momentum carries the lower armature away from the cores against the pressure of the upper spring which acts as a buffer.

The electrical action which ensues by this operation is as follows. With the parts in position as shown, the magnetic lines of force starting from one pole of the magnets flow through the adjacent pole piece to the core, downward through the portion of the core covered by the coil to the lower armature, across to the other

1

core, and up to the other pole piece and other pole of the magnets, thus completing the magnetic circuit. The magnetic lines cannot travel upward and through the upper armature because it is separated from the cores by air gaps and the lower path offers less resistance. The portion of the cores covered by the coils is therefore magnetized, the same as in the core of a jump-spark coil. When the armature bar released from the latch is at the end of its downward stroke, the armatures occupy the opposite positions with relation to the cores —that is, the upper one is in contact while the lower one is separated. The magnetic circuit through the lower part of the cores is thus broken while the top forms a bridge for the magnetic lines across the tops of the cores. The combined action of the two armatures causes a very sudden demagnetization of the cores covered by the coils, which thus induces a wave of current in the coils, as is done in an ordinary induction coil when its core is demagnetized by breaking the primary circuit. In this igniter the permanent magnets replace the battery and primary winding, while the armatures replace the vibrator and timer in interrupting the magnetic flow through the cores. The timing of the spark is accomplished by releasing the armature bar earlier or later in the stroke. This is done by shifting the position of the timing quadrant which in turn varies the position of the wedge so that it releases the latch earlier or later. The timing quadrant is provided with several notches into one of which the top of the wedge fits, thus holding the quadrant in the desired position. At one end of the quadrant there is a notch considerably deeper than the

others. This notch is so deep that when the wedge rests therein the latch is not tripped, and consequently the armature bar is not released and no spark is produced. In this position the quadrant acts as a switch and by mechanical means shuts off the current.

The advantages of this new form of igniter over rotating magnetos are numerous. It produces a hot spark at very high voltage for starting the engine, as the spark strength is entirely independent of the speed at which the engine is operated, and also because the voltage is strongest with the spark in its retarded or starting position. It is simple, strong, very compact, and dust-, oil-, and water-proof; moreover, it does away with all outside appliances and accessories such as switches, batteries, coils, wires, etc., the only wire exposed in the whole system being the short secondary wire leading from the igniter to the motor spark plug.

In using a jump-spark coil some method must be provided for interrupting or breaking the current in order to produce a spark in the induced current of the secondary winding. This is ordinarily accomplished by the use of what is known as a Vibrator. Fig. 81 represents a diagram of a jump-spark coil, and in this figure A is the core; B, the primary winding; C, the vibrator; D, the vibrator spring; E, the contact points; F, the adjusting screw; G, the condenser; H, the timer; and I, the secondary winding. As the core A is magnetized by the current passing around it in the primary winding B, the iron will, of course, be alternately magnetized and demagnetized as this current is made or interrupted. This intermittent magnetizing of the core