This article reports an investigation of the current and voltage characteristics of ``ignitor'' electrodes in a mercury pool rectifier (ignitron). Experiments were made on square rods of smooth homogeneous materials of various sizes and resistivities with the following results: (1) A frequency distribution curve is found for the voltage required by the ignitor which is approximately a Normal or Gaussian distribution. (2) The total current required for the ignition of an arc, divided by the perimeter is a constant, for a given material. (3) The total current required per unit length of perimeter times the square root of the resistivity is a constant. (4) For identical ignitors operated in parallel, the total current required is equal to the square root of the number of ignitors times the current required for one ignitor. (5) An expression is derived for the fraction of the total current which is useful in starting the arc and this is found to be inversely proportional to the square root of the width. This derivation is verified by the behavior of ignitors operated in parallel.