Topography of 101 Groundwater level 41 Ice sheets-- Formation of 74 History of 114 Movement of 75, 88 North American ice sheet 78 Igneous rock 18 Intermittent streams 42 Kames 115 Lakes-- Wisconsin Lake 129 Baraboo Lake 130 Devil's Lake 3, 9, 132, 137 Limestone, see Lower Magnesian. Lower Magnesian limestone-- Fossils of 12 History of 31-32 Occurrence of 11 Origin of 11 Position of 12 Structure of 8 Lower Narrows 5, 13, 67 Mantle rock 20, 144 Metamorphism 14, 24 Monadnocks 51 Moraines (see terminal moraine and ground moraine). Morainic aprons 119 Narrows 49 In quartzite 66, 67 Natural bridge 69 Navy Yard 69 Niagara limestone 33 North American ice sheet 78 Nunatak 89 Osars (see Eskers). Outwash plains 118, 120 Overwash plains 118, 120 Parfrey's Glen 10, 14, 29, 68 Peneplain 47, 50 Pewit's nest 9, 53, 69 Pine Hollow 69 Postglacial changes 146 Potsdam sandstone-- Fossils of 9, 11 History of 27-31