After a brief description of a new sand-tank laboratory and equipment for studying problems of the flow of fluids in porous materials, the remainder of the paper is devoted to an account of the application of a part of this equipment to a study of the flow of water between a pair of wells, such as is required for the determination of the permeability of the sand by the method described in part I. The potential distribution about the wells is found to conform sufficiently well with theory to justify the application of the analysis of part I, the interference due to the confining walls being satisfactorily negligible. The perturbation of the water table inseparable from the imposition of a potential difference between the wells is found not to invalidate the results based on an assumption of two-dimensional flow, while the corrections on account of the presence of a capillary fringe and a surface of seepage are satisfactorily made by adding to the measured depth of water in the well an increment equal to about half the thickness of the capillary fringe. The end correction for non-penetrating wells is also sufficiently well made by an addition to the measured depth of water; the magnitude of the correction is given for isotropic media for a well system of the dimensions used here, and the method of applying it to anisotropic media is indicated. The two-well method is used to estimate the permeability of the sand, which is then discussed in relation to the pore-size distribution. The elucidation of the permeability profile in a succession of strata is then discussed. Finally, techniques suited to work in the field are described, and a few preliminary fields results are quoted.
Correction: Facile synthesis of ultrathin Ni-MOF nanobelts for high-efficiency determination of glucose in human serum
