Nikola Tesla Books
HIGH FREQUENCY PLANT CULTURE Steel shaft longBosses turned up. from brass rod Rotor disc of zinc & diam. Detail of rotor and shaft Spring brass wires Straightened a soldered into stud Brass journal Lead 1' diam Casting Detail of bearing Section AA 163 Detail of brush & holder Fig. 18.-Details of the spark gap ranged to rotate in opposite directions at a fairly rapid rate of speed. The rotation serves the double purpose of always presenting a fresh sparking surface, and therefore a cool one, to the point of discharge, and in establishing a strong current of air directly upward and between the sparking surfaces, due to the surface friction of the periph ery of the discs. The effect of this current of air is to assist in the wiping out of any are which may form during the discharge. The discs are mounted upon a substantial framework and base of dry wood which has been painted with or preferably boiled in paraffin wax. The discs are mounted upon shafts of 2-inch steel and secured to the latter by means of brass bosses turned up and drilled to a snug fit on the shaft. When the final assembling has been done the bosses
