Point Discharge from a Tesla Pole

KNOBLAUCH. — An investigation of the following phenomenon: The discharge from a Tesla pole charges an insulated metallic plate positively at a certain distance and negatively at a greater distance. This is due to the greater speed and penetrative power of the negative ions. He has studied the distribution of the ions by means of perforated plates, and found that the positive charges are due to visible brush-discharges. When these brush discharges are prevented from impinging upon the plate by cutting out a central portion, no positive charge is obtained. The positive ions are strongest in the axial portion of the discharge. — Phys. Zeit., Dec. 15; abstracted in Lond. Elec., Jan. 4.