Within recent years, engineers and physicists engaged in studies of oil and gas production methods have increasing recognized the importance of the factors affecting the flow of fluids through porous media. In dealing with problems of fluid flow through reservoir sands, the permeability of porous media is , perhaps, the most significant factor and the one that recently has received a great deal of study. Qualitatively, permeability may be defined simply as fluid conductance or that property of the media that allows the flow of fluid through it. Quantitatively, permeability is not a simple property of a porous medium susceptible to direct physical measurement but a composite property that depends entirely on such physical properties of the medium as the volume of pore space (porosity), size and number of channels open to flow (grain size, arrangement and cementation), and characteristics of the walls of the flow channels (grain angularity, shape factors and roughness). Other physical properties and perhaps certain chemical characteristics of the porous medium may and probably do influence the permeability to some extent. With the exception of porosity however, none of the properties of a porous medium is susceptible to simple, direct measurement. In fact, few properties of a porous medium can be measured directly unless the medium is altered by crushing to such an extent that the permeability itself is changed. Crushing or breaking up a porous medium may permit measuring the grain size and amount of cementing material between the grains and may even enable an arbitrary measure of the angularity or shape of the grains to be established, but such methods are laborious and furnish no definite criteria either of the number an size of channels that might have been open to flow in the porous media in their original state or of the effect of different shapes of grains on flow of gases through the media/ Some of these properties of the media usually are dependent, also, upon the distribution of grains and cementing material, which obviously is changed when the medium is altered.