Lightning Made to Order (continued) Fig. 3. Compare the Size of the Tesla Coils Here Shown with That of the Man at the Left. A Double Exposure Was Necessary - First with the Man and Apparatus, Then with the Apparatus (Less the Man) Fully Excited. Sparks Measure 22 Feet in Length. Fig. 4. A Problem in Harmonics. Dr. Tesla Placed a Number of Inductance (Air Core) Coils Within the Large High Frequency Coil as Shown. Each Coil Resonated or Became Attuned to a Certain Harmonic of the Fundamental Oscillation. Glowing as Seen.