Laurentian Highlands, antiquity of, xiv, 235 Laurentide Glacier, iii, 238 Lava, iii, 380, xiv, 17-18; fissure flows, iii, 105-6; forms of fragments, xiv, 323-4; heat of molten, iii, 106-7; heat retention by, xv, 230; in Hawaiian craters, iii, 103, 104, 105, xiv, 322-3; porous, iii, 101 (see Pumice); rate of flow, 104-5; sheets, 102 (fig.); soils from, 28, xiv, 329; spine of Mount Pelee, iii, 103 Lava-dam Lakes, iii, 156 Lava Formations, xiv, 102-4, 164, 170, 172, 188; erosion effects, 103-5; extent of, iii, 106; in Appalachian trough, 212; in British Isles, 191; in Colorado, 177; in Columbian Plateau, 105-6, 227, 228, xiv, 102-3, 104, 164, 170, 172, 188; in Deccan of India, 105-6, 228, xiv, 103; in East Africa, 103; in Keewatin Series, iii, 169; in Lake Superior region, 177; in Snake River Valley, 228 Lava Rocks, not crystallized, iii, 170-1 Lavender, source, xiii, 205 Laveran, Alphonse, x, 155 Lavoisier, chemical work, xvi, 120, 121, 159-60, 177; combustion theory, viii, 34 Law, beginning of, xv, 360-3, 367-74, 379-80 Lawn Sprinklers, revolving, v, 143 Laxatives, use of, ix, 252 Lazear, Dr. Jesse W., x, 160, 162 Lead, affinity intensity, viii, 128; alloys with tin, melting point, iv, 161-2; atomic weight, viii, 189, 383; commercial source, iii, 330; compounds, viii, 29, 162; density of, iv, 113; extraction from ores, viii, 270, 271; from radium disintegration, 185; fusibility, 384; melting point and requirements, iv, 162; occurrence of, viii, 129; opaque to X-rays, vii, 250, 251; ores of, viii, 154, 198, 199-200; positiveness, vi, 59; production, iii, 362-3; properties, viii, 126-7, 154, 162; refining of, 272; refining, electrolytic, vii, 320; specific gravity, viii, 384; symbol, 383; test for, 287, 288; uses, iii, 362, viii, 162 Lead (of electric currents), vi, 171-4, 261, 262; angle of, vii, 362 Lead Arsenate, viii, 169 Lead Cells, vi, 130, 146-7, 150-1, viii, 167-9 Leaders, of crowds, xi, 332-3; of primitive peoples, xv, 363-6 Lead Pencils, graphite of, viii, 43 Lead Peroxide, in storage batteries, viii, 167-9 Lead Pipes, corrosion of, viii, 162 Leadville Mining District, iii, 363, 364 Leaf Mosaic, xiii, 38 Leafstalks, xiii, 34, 35 (fig.); light effect on, 87-8 Leakage, electrical, vii, 10-11, 371 Leaning Tower of Pisa, ii, 53, iv, 100-1; Galileo's use of, iv, 28, 97 Learning, Egyptian advice, xvi, 70; experience and, viii, 269 Learning Processes, xi, 33-46, 68; rules, 211-15 Leather, making of, viii, 257 Leather Collar, Maudsley's, v, 99