The existence of the threshold of EGD currents has been widely discussed in physics lately. Some physicists estimate the threshold voltage to be 300-1000 V. Current visual methods of investigating small velocities, comparable with the velocities of Brownian motion, do not provide unequivocal information. Neither do these methods permit to measure threshold voltage accurately. Complete elimination of thermogravital convection also presents a serious problem in making experiments. Nevertheless the bipolar structure of near-electrode regions serves as an indirect evidence of the existence of the threshold.