1. The Connecticut River undercuts the Hadley bank 2 2. Natural levees south of the Sunderland Bridge 2 3. Block diagram showing main features of central Massachusetts at the present time 5 4. Block diagram showing main features of central Massachusetts during recession of the Ice Sheet 5 5. Block diagram showing main features of central Massachusetts during excavation of the lowland 13 6. Block diagram showing main features of central Massachusetts after Triassic basins were filled 13 7. Map of Mount Toby showing gorges filled with conglomerate 20 8. Map showing agglomerate burying a fault scarp on Notch power line 24 9. Block diagram showing main features of central Massachusetts during volcanic stage 27 10. Block diagram showing the Triassic basins of central Massachusetts 27 11. Map of old volcanic region near Mount Hitchcock and west of the Notch 29 12. Block diagram showing topography during formation of the lead veins 31 13. Block diagram of region during Middle Ordovician time 39 14. Block diagram of region at end of Ordovician time 39 15. Block diagram of region during Devonian period 39 16. Block diagram of region during Carboniferous period 41 17. Block diagram of region in early Triassic time 41 18. Block diagram of region in late Triassic time 41 19. Block diagram of region at opening of Cenozoic era 45 20. Block diagram of region at the present time 45 21. Map showing location of interesting places 53 22. Meander scarps at edge of flood plain, Sunderland 57 23. Map of the Leverett lead veins 65 24. Diagrams showing development of Notch and Notch Mountain 74 Introduction