INVENTIONS OF NIKOLA TESLA.

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It lias been asserted by competent English electricians that in aconstant-current machine or transformer the regulation is effectedby varying the phase of the secondary current. That this viewis erroneous may be easily proved by using, instead of lamps, de-vices each possessing self-induction and capacity or self-inductionand resistance—that is, retarding and accelerating components—in such proportions as to not affect materially the phase of thesecondary current. Any number of such devices may be insertedor cut out, still it will be found that the regulation occurs, a con-stant current being maintained, while the electromotive force isvaried with the number of the devices. The change of phase ofthe secondary current is simply a result following from thechanges in resistance, and, though secondary reaction is alwaysof more or less importance, yet the real cause of the regulationlies in the existence of the conditions above enumerated. Itshould be stated, however, that in the case of a machine the aboveremarks are to be restricted to the cases in which the machine isindependently excited. If the excitation be effected by commu-tating the armature current, then the iixed position of the brushesmakes any shifting of the neutral line of the utmost importance,and it may not be thought immodest of the writer to mentionthat, as far as records go, he seems to have been the first who hassuccessfully regulated machines by providing a bridge connectionbetween a point of the external circuit and the commutator bymeans of a third brush. The armature and field being properlyproportioned and the brushes placed in their determined posi-tions, a constant current or constant potential resulted from theshifting of the diameter of commutation by the varying loads.

In connection with machines of such high frequencies, thecondenser affords an especially interesting study. It is easy toraise the electromotive force of such a machine to four or fivetimes the value by simply connecting the condenser to the cir-cuit, and the writer has continually used the condenser for thethe purposes of regulation, as suggested by Blakesley in his bookon alternate currents, in which he has treated the most frequentlyoccurring condenser problems with exquisite simplicity and clear-ness. The high frequency allows the use of small capacities andrenders investigation easy. But, although in most of the experi-ments the result may be foretold, some phenomena observed seemat first curious. One experiment performed three or four monthsago with such a machine and a condenser may serve as an il-