In the early spring of 1950, the writer began a detailed study of the drainage patterns of the folded Appalachian mountains in Pennsylvania and Virginia. The study was undertaken in order to find if the nature of the folds (anticlinal or synclinal) could be determined by the drainage patterns alone.
During this study, the writer noticed several drainage basins wherein the longitudinal subsequent stream flowed markedly closer to one of the flanking ridges than to the other. It was noticed that the ridge nearer the stream was lower than the opposite ridge. This phenomenon was well developed in anticlinal valleys. Further investigation showed that, in each anticline, the higher ridge was underlain by rocks dipping more gently than those underlying the lower ridge.