The southern part of the basin was deepened, and the highlands were rejuvenated spasmodically from Springfield to New Haven. The sinking of the lowland on the west and the rising of the highlands on the east took place along a fracture plane, commonly called “the eastern border fault,” near the eastern limits of the red sediments throughout that part of the valley. The rocks composing the alluvial fans are flexed sharply downward east of Portland, Connecticut, like compressed pages in a book, where the great eastern mountain block pushed obliquely against them. In this way the mountain range was renewed as erosion wore it away, and the basin was deepened periodically as the wash from the highlands filled it. The intermittent uplift sustained the growth of the fans along the edge of the lowland, but the frequent recurrence of movement never permitted these graded accumulations of waste to extend far out from their mountain sources. The great fracture, which sharply delimits rocks of different origins, and the deformation in the strata near Portland record, as surely as the writings of any human historian, a tale of periodic rock compression and paroxysmal release that must have been accompanied by violent tremors. Connecticut and Massachusetts had their earthquakes and had them as violent as any now originating in the western ranges of the United States and Mexico; but happily they shook a land which was overrun by the dinosaurs, and which was not yet ready for human habitation. [Illustration: Fig. 7. _Map of Mount Toby showing gorges filled with conglomerate._]