Among the most notable features of the geology of Yorkshire are two parallel structures known as the Cleveland and Market Weighton anticlines. Although they are parallel and not far distant, it has often been pointed out, and especially by Kendall and Lamplugh that these structures differ in almost every possible way. The Market Weighton axis has now no topographical expression at the surface, whereas the Cleveland axis forms the watershed of one of the most clearly developed river-systems of the country. The first and most obvious meaning of this is that the Cleveland axis moved during the Tertiary, while the Market Weighton axis did not. But the real fundamental difference goes much further back than that.