We use thermal imaging of Joule heating to see for the first time electrical
conducting paths created by the so-called Branly effect in a two-dimensional
metallic granular medium (aluminium). Multiple breakdowns are shown to occur
when the medium is submitted to high voltage increases (more than 500 V) with
rise times close to one hundred of microseconds.Comment: 4 pages, 5 figures, related informations at
http://chemphys.weizmann.ac.il/~damien/index.htm