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INVENTIONS OF NIKOLA TESLA.

shall presently endeavor to illustrate. In presenting this secondclass of electrical effects, I will avail myself principally of suchas are producible without any return circuit, hoping to interestyou the more by presenting these phenomena in a more or lessnovel aspect.

It has been a long time customary, owing to the limitedexperience with vibratory currents, to consider an electric cur-rent as something circulating in a closed conducting path. Itwas astonishing at first to realize that a current may flow throughthe conducting path even if the latter be interrupted, and itwas still more surprising to learn, that sometimes it may beeven easier to make a current flow under such conditionsthan through a closed path. But that old idea is gradually disappearing, even among practical men, and will soon be entirelyforgotten.

If I connect an insulated metal plate p, Fig. 175, to one of theterminals t of the induction coil by means of a wire, though this

Fig. 175.

plate be very well insulated, a current passes through thewire when the coil is set to work. First I wish to give youevidence that there is a current passing through the connectingwire. An obvious way of demonstrating this is to insert betweenthe terminal of the coil and the insulated plate a very thin plati-num or german silver wire w and bring the latter to incandes-cence or fusion by the current. This requires a rather large plateor else current impulses of very high potential and frequency.Another way is to take a coil c, Fig. 175, containing many turns ofthin insulated wire and to insert the same in the path of the cur-rent to the plate. When I connect one of the ends of the coil to thewire leading to another insulated plate p l5 and its other end to theterminal of the induction coil, and set the latter to work, a cur-rent passes through the inserted coil c and the existence of thecurrent may be made manifest in various ways. For instance, I