An hypothesis of the origin and accumulation of oil and gas fields, arrived at from the data of soil analysis, is presented. This hypothesis also offers an explanation of the quite different concentrations of subsurface waters in different geologic provinces. Furthermore, it seeks to explain the variation of type of accumulation with respect to depth below the surface and deformation of the sediments in which the accumulation occurs. Lastly, the value of the method of soil analysis as an exploration device is indicated.