HIGH FREQUENCY AND HIGH POTENTIAL CURRENTS. 165

tively, the air molecules not necessarily coming in contact witlithe ball, though they undoubtedly do so. To convince ourselvesof this we only need to exalt the condenser action, for instance,by enveloping the ball, at some distance, by a better conductorthan the surrounding medium, the conductor being, of course,insulated; or else by surrounding it with a better dielectric andapproaching an insulated conductor; in both cases the streamswill break forth more copiously. Also, the larger the ball witha given frequency, or the higher the frequency, the more willthe ball have the advantage over the point. But, since a certainintensity of action is required to render the streams visible, it isobvious that in the experiment described the ball should not betaken too large.

In consequence of this two-fold tendency, it is possible to pro-duce by means of points, effects identical to those produced by

Fig. 100. Fig. 110.

capacity. Thus, for instance, by attaching to one terminal ofthe coil a small length of soiled wire, presenting many pointsand offering great facility to escape, the potential of the coilmay be raised to the same value as by attaching to the terminala polished ball of a surface many times greater than that of thewire.

An interesting experiment, showing the effect of the points,may be performed in the following manner: Attach to one ofthe terminals of the coil a cotton covered wire about two feet inlength, and adjust the conditions so that streams issue from thewire. In this experiment the primary coil should be preferablyplaced so that it extends only about half way into the secondarycoil. How touch the free terminal of the secondary with a con-ducting object held in the hand, or else connect it to an insulated