It has been proved that in the flow of liquids the resistance to flow depends, first, upon the size of the individual particles of which the liquid is composed and, second, upon the spacing of the particles, this latter being dependent upon the conditions of temperature and pressure. As the size of the particles is increased and the Brownian motion of the particles becomes less and less, the above statement cannot be accepted as applicable without supporting evidence. However, if the laws of flow of materials like powdered coal, cement, etc., were known, there might be developed an improved method for obtaining the average particle size. The sizes of the particles and their method of spacing will presumably determine questions concerning rates of settling, caking together, and the seepage of both gases and liquids in or out of the materials. In a preliminary investigation, it seemed best to begin with dry sand and capillaries of known lengths and radii, using various temperatures.