The electrical resistance of a metallic granular packing has been recorded at room temperature. A nearby burster between which sparks are produced, induces a decrease in the resistance of the granular packing as described in the works of Branly. Our measurements emphasize that the decrease is continuous and the resistance variations behave like a stretched exponential law due to the creation of new electrical paths as in nucleation-growth soldering processes. This behavior has been identified to be a diffusionlike process.

• Received 20 December 2002

DOI:https://doi.org/10.1103/PhysRevE.67.040302