HIGH FREQUENCY AND HIGH POTENTIAL CURRENTS. 235

induction, and then it would be necessary to employ a muchhigher frequency and potential. Neither would be advisable, fora higher potential would endanger the insulation of the smallprimary coil, and a higher frequency would result in a materiallydiminished torque.

It should be remarked that when such a motor with aclosed secondary is used, it is not at all easy to obtain rota-tion with excessive frequencies, as the secondary cuts offalmost completely the lines of the primary—and this, ofcourse, the more, the higher the frequency—and allows the pass-age of but a minute current. In such a case, unless the second-ary is closed through a condenser, it is almost essential, in orderto produce rotation, to make the primary and secondary coilsoverlap each other more or less.

But there is an additional feature of interest about this motor,namely, it is not necessary to have even a single connection be-tween the motor and generator, except, perhaps, through theground; for not only is an insulated plate capable of giving offenergy into space, but it is likewise capable of deriving it froman alternating electrostatic field, though in the latter case theavailable energy is much smaller. In this instance one of themotor terminals is connected to the insulated plate or bodylocated within the alternating electrostatic field, and the otherterminal preferably to the ground.

It is quite possible, however, that such “ no wire ” motors, asthey might be called, could be operated by conduction throughthe rarefied air at considerable distances. Alternate currents,especially of high frequencies, pass with astonishing freedomthrough even slightly rarefied gases. The upper strata of the airare rarefied. To reach a number of miles out into space requiresthe overcoming of difficulties of a merely mechanical nature.There is no doubt that with the enormous potentials obtainable bythe use of high frequencies and oil insulation, luminous dischargesmight be passed through many miles of rarefied air, and that, bythus directing the energy of many hundreds or thousands of horse-power, motors or lamps might be operated at considerabledistances from stationary sources. But such schemes are men-tioned merely as possibilities. We shall have no need to transmitpower in this way. We shall have no need to transmit powerat all. Ere many generations pass, our machinery will be drivenby a power obtainable at any point of the universe. This idea is