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INVENTIONS OF NIKOLA TESLA.

with closed conductors, synchronizing motors, and rotating heldtransformers:—

The subject which I now have the pleasure of bringing toyour notice is a novel system of electric distribution and trans-mission of power by means of alternate currents, affording pecu-liar advantages, particularly in the way of motors, which I amconfident will at once establish the superior adaptability of thesecurrents to the transmission of power and will show that manyresults heretofore unattainable can be reached by their use ; re-sults which are very much desired in the practical operation ofsuch systems, and which cannot be accomplished by means ofcontinuous currents.

Before going into a detailed description of this system, I thinkit necessary to make a few remarks with reference to certain con-ditions existing in continuous current generators and motors,which, although generally known, are frequently disregarded.

In our dynamo machines, it is well known, we generate alter-nate currents which we direct by means of a commutator, a com-plicated device and, it may be justly said, the source of most ofthe troubles experienced in the operation of the machines, hfow,the currents so directed cannot be utilized in the motor, butthey must—again by means of a similar unreliable device—be reconverted into their original state of alternate currents.The function of the commutator is entirely external, and in noway does it affect the internal working of the machines. Inreality, therefore, all machines are alternate current machines,the currents appearing as continuous only in the external circuitduring their transit from generator to motor. In view simply ofthis fact, alternate currents would commend themselves as a moredirect application of electrical energy, and the employment ofcontinuous currents would only be justified if we had dynamoswhich would primarily generate, and motors which would bedirectly actuated by, such currents.

But the operation of the commutator on a motor is twofold;first, it reverses the currents through the motor, and secondly,it effects automatically, a progressive shifting of the poles of oneof its magnetic constituents. Assuming, therefore, that both ofthe useless operations in the systems, that is to say, the directingof the alternate currents on the generator and reversing the directcurrents on the motor, be eliminated, it would still be necessary,in order to cause a rotation of the motor, to produce a progressive