Magnesian limestone, 19, 47 Magnesium, 13 Mammoth, 56 Man-- recently created, 59 as an agent in producing geological changes, 101 impressions of the feet of, 59 skeleton of from Guadaloupe, 59 Manganese, 12 Marine currents, 108 Marine currents, cause of, 109 abrading power of, 111 Marl, 19 Mastodon, 55 Megatherium, 55 Metamorphic changes, 67 Metamorphic rocks, 30 amount of, 67 origin of, 134 order of superposition, 31 upper limit variable, 13 localities of, 32 Metallic ores, 92 Mica, 14 slate, 18, 31 Millstone grit, 40 fossils of, 41 becomes coal measures, 42 Mineral-- definition of, 13 Mineral veins, 69 formation of, 100 Modern formation, 57 why but little known, 57 fossils, 57 Moisture of the atmosphere a disintegrating agent, 96 Monte Nuovo, 26 Mount Loa, eruption of, 26 N. Neocomian system, 52 New red sandstone, 47 fossils of, 48 ores of, 47 geographical range of, 49 Niagara Falls, how preserved, 106 Nitrogen, 11 Nummulite rock, 54 O.