POL mi ASK CURRENTS.

89

tor in which by means of one or more alternating currents hehas produced the rotation or progression of the magnetic poles.

This new mode of operation wall now be described. Fig. 72is a side elevation of such motor. Fig. 73 is a side elevation ofa more practicable and efficient embodiment of the invention.Fig. 74 is a central vertical section of the same in the plane ofthe axis of rotation.

Referring to Fig. 72, let x represent a large iron core, whichmay be composed of a number of sheets or laminae of soft ironor steel. Surrounding this core is a coil y, which is connectedwith a source e of rapidly varying currents. Let us consider now

Figs. 72 and 73.

the magnetic conditions existing in this core at any point, as b,at or near the centre, and any other point, as a, nearer the sur-face. When a current impulse is started in the magnetizing coily, the section or part at a, being close to the coil, is immediatelyenergized, while the section or part at b, which, to use a conveni-ent expression, is “protected” by the intervening sections orlayers between a and b, does not at once exhibit its magnetism.However, as the magnetization of a increases, b becomes alsoaffected, reaching finally its maximum strength some time laterthan a. Upon the weakening of the current the magnetizationof a first diminishes, while b still exhibits its maximum strength;