Looming, optical, i, 172, 174, 376 Looms, history and development, v, 268, 277-82, xv, 245-7; various inventions, v, 376-7, 381, 383 Loons, xii, 250 Loop-the-loop Cars, iv, 74 Loosestrife, xiii, 140-1, 203 Lop-Nor Desert, xiv, 209 Lorentz, light theory, xvi, 137-8; relativity theory, iv, 18, xvi, 196 Lories, Australian, xii, 266-7 Los Angeles, electric power supply, v, 81, vi, 363; telephone connection with New York, 367-8 Loudness, of sound, iv, 211; to what due, xi, 104 Louis XIV, high heels introduced by, x, 306; observatory founded by, ii, 58; on Pyrenees Mts., xiv, 239 Louis, Pierre C. A., x, 108 Louisiana cotton, xiii, 237; salt deposits, viii, 140; sulphur deposits, 76 Louisiana Purchase, xiv, 192, 193, 311 Louisville, early growth, xiv, 219; water supply, viii, 318 Loup Fork, xiv, 161 Love, fundamental impulse, xv, 185; motor character, xi, 58; sentiment of, 149-50; unknown to savages, xv, 279, 321 Lowbrows, xv, 43 Lowell, Percival, ii, 233-4, 237, 271; reference to, xi, 218 Lowell Observatory, ii, 146-7, 148 Low German, xv, 162 Lowlands, xiv, 213 Lows, Low Pressure Areas, i, 135-6, 137, 376; of Iceland, 361; movement, 134-5, 237; physiological effects, 330; thunderstorms and, 138; wind and weather attendants, 125, 218, 236, 237 (see also Pressure Areas) Lubricants, fatty, viii, 247; graphite, 43, vii, 308, 309; oil-dag, 300 Luciferin, xii, 20 Lues, curability of, x, 134; germ of, 195, 199; immunity to, 207 Lumber, chief source of, xiv, 383; from heartwood, xiii, 25 Lumen, light unit, iv, 352 Luminous Plants and Animals, i, 346-7, xii, 20, xiii, 203-4, xvi, 144, 146 Lunation, defined, ii, 196 Lundy, Lake, iii, 149 Lung Fish, iii, 283 (fig.), xii, 164-6 Lungs, ix, 254-6; aeration of blood by, 253, x, 62, 63, 331; carbon dioxide diffusion by, ix, 263-7; circulation of blood through, 196 (fig.), 198-200; congestion of, x, 341; development in black and white races, xv, 50; diseases of, susceptibility to, 50, 51; dust in, ix, 223; evolution in animal kingdom, xii, 164-5, 169, 187, 248; external respiration by, x, 339; functions in maintenance of life, ix, 21-3; infection through, x, 198, 220; in pneumonia, 289; oxygen supply through, ix, 51 (diagram), 253, 258; poisons exhaled by, 269; water loss by, i, 317, ix, 274 Lupine, leaves, xiii, 113 Luray Caverns, iii, 127, xiv, 148 "Lusitania," loss of, xi, 332 Luster, of metals, viii, 126; of minerals, 201 Lycopodium Selago, xiii, 305-6, 322 Lycopods, iii, 253-4, 256 Lye, making of, viii, 276, 278; in soap-making, 221 Lyell, geological work, xvi, 126, 171 Lymphatics, ix, 222-5; in circulatory system, 196 (fig.) Lynx, xii, 364-5