836

INVENTIONS OF NIKOLA TESLA.

through a condenser c of small capacity, and the other directly.The primaries are provided with secondaries s t and s 3 which arein series with the energizing circuits, a 2 and b 2 and a motor m s ,the condenser g again serving to produce the requisite differencein the phase of the currents traversing the motor circuits. Assuch phase motors with two or more circuits are now well knownin the art, they have been here illustrated diagrarnmaticaily. dSTodifficulty whatever is found in operating a motor in the mannerindicated, or in similar ways; and although such experiments upto this day present only scientific interest, they may at a periodnot far distant, be carried out with practical objects in view.

It is thought useful to devote here a few remarks to the sub-ject of operating devices of all kinds by means of only one leadingwire. It is quite obvious, that when high-frequency currents aremade use of, ground connections are—at least when the e. m. f.of the currents is great—better than a return wire. Such groundconnections are objectionable with steady or low frequency cur-rents on account of destructive chemical actions of the formerand disturbing influences exerted by both on the neighboring cir-cuits ; but with high frequencies these actions practically do notexist. Still, even ground connections become superfluous whenthe e. m. f. is very high, for soon a condition is reached, when thecurrent may be passed more economically through open, thanthrough closed, conductors. Remote as might seem an industrialapplication of such single wire transmission of energy to one notexperienced in such lines of experiment, it will not seem so toanyone who for some time has carried on investigations of suchnature. Indeed I cannot see why such a plan should not bepracticable. ISior should it be thought that for carrying out sucha plan currents of very high frequency are expressly required,for just as soon as potentials of say 30,000 volts are used, thesingle wire transmission may be effected with low frequencies,and experiments have been made by me from which these infer-ences are made.

When the frequencies are very high it has been found in lab-oratory practice quite easy to regulate the effects in the mannershown in diagram Fig. 181. Here two primaries p and P! are shown,each connected with one of its ends to the line l and with theother end to the condenser plates c and c, respectively. Nearthese are placed other condenser plates C! and c 1? the former be-ing connected to the line n and the latter to an insulated larger