means of obtaining Continuous Electrical Oscillations. 257 



the glow-lamp remains fairly steady, and if its incandescent 

 filament is examined in a revolving mirror, its image will be 

 seen spread out into a uniform band of light. 



This, however, is not an absolute proof of the uniformity 

 of the oscillatory current. To the above-mentioned condenser 

 circuit, I then attached a long helix of fine silk-covered 

 wire (No. 30 S.W.Gr.) wound in one layer of closely 

 adjacent turns on an ebonite tube (see fig. 2). The length 



of this helix was 210 cms., its diameter 4' 78 cms., and the 

 number of turns 5470. This helix was supported horizontally 

 on insulating stands about 45 cms. above the table, a sheet 

 of zinc as long as the helix being placed on the table to act 

 as an earth plate. This earth plate was connected to the 

 metallic electrode of the arc and the helix to the junction 

 point between the condenser and inductance coils in series 

 with it. 



The far end of the helix was provided with a number of 

 needle-points formed by a bunch of sewing- needles attached 

 to a wire. 



On adjusting the inductance in series with the condenser 

 so that the whole inductance in series across the arc terminals 

 had a value of about 215,000 cms., powerful stationary 

 oscillations were excited in the helix. Under these conditions^ 

 vivid blue electric brushes 1 or 2 cms. long appear on the 

 needle-points at the far end of the helix, thus showing that 

 the potential at that end has been increased by resonance to 

 many thousand volts. These brushes are not of the same 

 harmless character as the ordinary electric brush of an 

 electrostatic machine, but are veritable flames or arcs 

 taking place into the air. They are very hot and will melt 

 sealing-wax and set fire to paper, and inflict the most painful 



