mVEXTIOXS OF NIKOLA TKSLA.

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one single helix, as shown in the drawings. The part x' beingnormally in circuit, is, with the tine wire upon the shunt-magnet,wound and traversed by the current in the same direction, so asto tend to produce similar poles, x n or s s, on the correspondingpole-pieces of the magnets m and x. The part // is only in cir-cuit when the lamp is cut out, and then the current being in theopposite direction produces in the main magnet, magnetism ofthe opposite polarity.

The operation is as follows: At- the start the carbons are tohe in contact, and the current passes from the positive binding-post, k to the lamp-frame, carbon-holder, upper and lower carbon,insulated return-wire in one of the side rods, and from therethrough the part x' of the wire on the main magnet to the nega-

Fig. 289.

tive binding-post. Upon the passage of the current the mainmagnet is energized and attracts the clamping-armature g , swing-ing the clamp and gripping the rod by means of the grippingjaws e e. At the same time the armature level 1 l is pulled downand the carbons are separated. In pulling down the armature leverl the main magnet is assisted by the shunt-magnet x, the latterbeing magnetized by magnetic induction from the magnet m.

It will be seen that the armatures i, and g are practically thekeepers for the magnets m and x, and owing to this fact bothmagnets with either one of the armatures l and g may be con-sidered as one horseshoe magnet, which we might term a “ com-pound magnet.” The whole of the soft-iron parts m, m’, g , n',x and i, form a compound magnet.