Fig. 1. Initial experiment of Silliman et al. (2002) demonstrating transport within a homogeneous sand. Flow is from left to right and the dye is introduced at the locations shown by the circles. Transport above the water table (the water table is shown by the dotted line) is evident in the motion of the dye spots. The arrows show the association between each dye spot and the location of injection of that spot. The time reported on the figure is time since the introduction of the dye tracer. (After Silliman et al., 2002.)