Nikola Tesla Books
Colorado Springs
Sept. 19, 1899
Various arrangements with oscillator and extra coil for production of most powerful disturbances.
All of these arrangements have been experimented with and described before, and so far the plan illustrated in Diagram 4. seems to be best. In Fig. 1. the extra coil is merely a means of increasing pressure on the end. In Figs. 2. and 3. the vibrations through the ground are intensified by the extra coil working directly on the ground either through a gap with capacity or without same.
In all cases it has been found important to have the two systems vibrate in synchronism. The same considerations apply to Diagrams 4, 5 and 6. The plan in Fig. 4. being found best, the question is what is the best length to give to the wires.
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