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INVENTIONS OF NIKOLA TESLA.

jars were made to discharge over a single or multiple gap throughthe primary of the second coil. To insure the action of the gap,the arc was blown out by a magnet, or air blast. To adjust thepotential in the secondary a small oil condenser was used, orpolished brass spheres of different sizes were screwed on theterminals and their distance adjusted.

When the conditions were carefully determined to suit eachexperiment, magnificent, effects were obtained. Two wires,stretched through the room, each being connected to one of theterminals of the coil, emitted streams so powerful that the lightfrom them allowed distinguishing the objects in the room ; thewires became luminous even though covered with thick andmost excellent insulation. When two straight wires, or two con-centric circles of wire, are connected to the terminals, and set atthe proper distance, a uniform luminous sheet is produced be-tween them. It was possible in this way to cover an area ofmore than one meter square completely with the streams. Byattaching to one terminal a large circle of wire and to the otherterminal a small sphere, the streams are focused upon the sphere,produce a strongly lighted spot upon the same, and present, theappearance of a luminous cone. A very thin wire glued upon aplate of hard rubber of great thickness, on the opposite side ofwhich is fastened a tinfoil coating, is rendered intensely luminouswhen the coating is connected to the other terminal of the coil.Such an experiment can be performed also with low frequencycurrents, but much less satisfactorily.

When the terminals of such a coil, even of a very small one,are separated by a rubber or glass plate, the discharge spreads,over the plate in the form of streams, threads or brilliant sparks,and affords a magnificent display, which cannot be equaled bythe largest coil operated in the usual ways. By a simple adjust-ment it is possible to produce with the coil a succession of bril-liant sparks, exactly as with a Holtz machine.

Under certain conditions, when the frequency of the oscillationis very great, white, pliantom-like streams are seen to break forthfrom the terminals of the coil. The chief interesting- featureabout, them is, that they stream freely against the outstretchedhand or other conducting object without producing any sensa-tion, and tlie hand may be approached very near to the terminalwithout a spark being induced to jump. This is due presumablyto the fact that a considerable portion of the energy is carried