Permeability of a variety of coarse noncohesive granular materials tested in a 22 inch diameter permeameter. Velocity/hydraulic gradient relationship plotted, yielding a series of straight lines with sharp discontinuities of slope between each regime, rather than a curved transition from the low Darcy-type flow to the high turbulent flow region. For each material and its packing, the V-S relationship is characterised by a discontinuous exponential relationship. The upper limit of Darcy's law could be predicted more accurately from a correlation between coefficient of permeability and limited hydraulic gradient than from a Reynolds number. No method of predicting the lower limit of validity of Darcy's law is apparent.