Nikola Tesla Books
226 HIGH FREQUENCY APPARATUS stool the performer approaches the ball discharger of the transformer with the lights out and the coil in operation. As the rod nears the ball, a beautiful halo or luminous vapor gathers at the point and increases in intensity as the distance is shortened. Finally, when the rod is within four or five feet of the ball, an enormous sheet of purplishwhite flame crashes across the intervening space and into the rod held in the hands. The spark leaps into the air and breaks as the heat causes it to rise, and the moment the discharge is broken another flame takes its place. If the distance is shortened to within six inches or a foot of the ball, a piece of stick or bit of paper held in the spark will be ignited immediately. The performer may then withdraw and have the current turned off for a few words of explanation. The next experiment may be made to show that the current is actually going into the body of the entertainer. To this end, he approaches the ball with his rod held in one hand and in the other he grasps an electrode to which is connected a wire leading to one terminal of an incandescent lamp. The other terminal of the lamp is attached to a second electrode which is held by the assistant. When the current is turned on the spark leaps to the rod as before and the lamp is lighted to full incandescence or even burned out by the current passing between the bodies of the performer and his assistant standing nearby. Some of the most startling and spectacular experiments of which the high frequency apparatus is capable are produced in connection with the insulated stool and the charged body of the performer. For most of these experiments, the frequency of the current should be increased by moving the primary clip of the oscillation transformer to a point where fewer turns are included in the circuit. This will reduce the spark length of the coil, but this loss can
