Nikola Tesla Books
228 HIGH FREQUENCY APPARATUS uum tube brought to within even six or eight feet of the charged body lights up with its characteristic glow, and, when it approaches to within a foot of the body, the glow is practically as bright as it would be if the current were passing into it through a wire instead of through space. An entertaining experiment is to bring an incandescent lamp bulb, held by its base in the assistant's hand, close to a rod held in the hand of the performer. The current slowly strikes through the glass wall, and, as the fracture increases, the air is let into the bulb. As the vacuum lowers the color of the glow in the bulb changes from bluish white to red, then to purple and finally it disappears as the spark punctures the wall and finds its way to the wires inside. No further attempt will be made to describe "experiments" for to do so is futile at this point. The worker will find that every time he turns the current on, he finds some new wrinkle or stunt to do with the spark. Ardent experimentation with the apparatus itself is the very best teacher and a day spent merely in "playing" with the outfit will give the ingenious worker scores of fascinating experiments, some of which are suitable for the stage and others for the parlor or the laboratory. Dr. Tesla prepared a series of intensely interesting lectures some years ago and his work, now in book form,* offers a truly remarkable series of instructive experiments. While Dr. Tesla advocates, in his book, the use of a high frequency alternator or else an oil-immersed oscillation transformer, still many, if not all, of the performances he pictures can be shown with the apparatus described in this book. * Experiments with Alternating Currents at High Potentials and High FrequenciesTesla-$1.00.
