A series of tests of samples from different parts of the United States indicate that the average porosity of pure quartz sandstones progressively decreases, and the average crushing strength progressively increases, as the degree of carbonization of the associated coals becomes greater. Since the amount of regional alteration, as indicated by the degree of carbonization of the coals, is known to be on considerable importance in predicting the oil and gas possibilities of untested areas, it appears that average porosity and crushing strength could be utilized to estimate the possibilities of strata not associated with coals. Before any extensive practical use of the method can be made, however, it will be necessary to make a large number of tests to determine as accurately as possible the porosity and crushing strength corresponding to each degree of carbonization of the associated coals.