482

INVENTIONS OF NIKOLA TESLA.

stration before the Society of Arts in Boston, by Prof. Anthony.Another curious exhibit is shown enlarged in Fig. 301. Thisconsists of thick discs of wrought iron placed lengthwise, with amass of copper cast around them. The discs were arrangedlongitudinally to afford an easier starting by reason of the inducedcurrent formed in the iron discs, which differed in phase fromthose in the copper. This armature would start with a single cir-cuit and run in synchronism, and represents one of the earliesttypes of such an armature. Fig. 305 is another striking exhibit.

Fig. 800. Fig. 301. Fig 302.

Fig. 303. Fig. 304. Fig. 305.

Fig. 306 Fig. 307 Fig. 308.

Fig. 309. Fig. 310.

This is one of the earliest types of an armature with holes beneaththe periphery, in which copper conductors are imbedded. Thearmature has eight closed circuits and was used in many differentways. Fig. 304 is a type of synchronous armature consisting ofa block of soft steel wound with a coil closed upon itself. Thisarmature was used in connection with the field shown in Fig. 298and gave excellent results.

Fig. 302 represents a synchronous armature with a large coilaround a body of iron. There is another very small coil at rightangles to the first. This small coil was used for the purpose of