PERSONAL EXHIBIT AT T1W WORLD’S FAIR.

481

of the rotating field in one of the elements of the motor by currents differing in phase and energizing the other element bydirect currents. The armatures are of the two and three phasetype, k is a model of a motor shown in an enlarged view in Fig.298. This machine, together with that shown in Fig. 299, wasexhibited at the same lecture, in May, 1888. They werethe first rotating field motors ■which were independently tested,having for that purpose been placed in the hands of Prof. An-thony in the winter of 1887-88. From these tests it was shownthat the efficiency and output of these motors was quite satisfac-tory in every respect.

It was intended to exhibit the model shown in Fig. 299, but itwas unavailable for that purpose owing to the fact that it was

Fig. 299 .

some time ago handed over to the care of Prof. Ayrton in Eng-land. This model was originally provided with twelve independ-ent coils; this number, as Mr. Tesla pointed out in his first lec-ture, being divisible by two and three, was selected in order to makevarious connections for two and three-phase operations, and duringMr. Tesla’s experiments was used in many ways with from two tosix phases. The model, Fig. 298, consists of a magnetic frame oflaminated iron with four polar projections between which an arm-ature is supported on brass bolts passing through the frame. Agreat variety of armatures was used in connection with these twoand other fields. Some of the armatures are shown in front onthe table, Fig. 297, and several are also shown enlarged in Figs.300 to 310. An interesting exhibit is that shown at l, Fig. 297.This is an armature of hardened steel which was used in a demon-