The anode arc is a source of erosion in electrical contacts. The erosion is thought to be proportional to the arc duration. This paper investigates the anodic arc length. A new experimental technique is described to measure arc duration. This method provided better statistics and better time resolution. By applying this technique to different metals, the experimental fact that these arcs are a succession of bursts of fixed duration became evident, The distribution of the number of arcs versus their length can be discussed in terms of the average number of bursts per unit time. Only two parameters for a given metal are sufficient to calculate the average arc length in any given circumstance. A classification o': different metals versus their tendency to sustain long anode arcs is presented.