CONSIDERABLE use has been made of the following power law for expressing the size distribution of particles1–3 : where N is the number of particles below diameter D. The distributions have been displayed as plots of dN/dD against D on logarithmic axes which give straight lines of slope −γ. The positions of the lines have been arbitrarily adjusted in the belief that K was merely a concentration factor3. This supposition is erroneous with the result that distributions which have been published in this form cannot be interpreted by a reader.