Porosities were determined of 98 samples of unweathered sandstones collected in the Ouachita Mountains, the Arkansas Valley, and the Ozark Plateaus of Arkansas. The average porosity in the intensely folded beds of the Ouachita Mountains was found to be 5.7 per cent, in the beds of the less folded Arkansas Valley, 7.8 per cent, and in the comparatively unfolded beds of the Ozark Plateaus, 10.9 per cent. The average degree of inclination of the folded beds in the Ouachita Mountains from incomplete figures, is estimated to be 54.1°; in the Arkansas Valley, 17.0°; and in the Ozark Plateaus, 5.1°, thus indicating the relationship between the average regional porosities of the sandstones and the average deformation of the folded beds. It appears probable that, if sufficient data were accumulated, a useful relationship could be established between the average regional porosities of the sandstones and the average regional carbon ratios of the coal in western Arkansas.