Arid Regions, alkali deposits, viii, 139; dust whirls, i, 60; mineral matter in waters, viii, 196; plants of, xv, 18-9; rainfall of, i, 109, 112; rock weathering in, xiv, 41-2, 51-2, 77-9, 124; soils of, 68-9, 383 (see also Deserts) Aristarchus of Samos, ii, 10, 27-8 Aristillus, ii, 28-9, 31 Aristocracy, changing ideas of, xv, 377 Aristocratic Type, xiii, 356 Aristotle, association principles, xi, 197-8; authority in Middle Ages, ii, 33, 42; conception of cosmos, ii, 367; lectures on fossils, etc., xvi, 168; medical work of, x, 23, 27, 74; meteorological treatise, i, 67; monad theory, xvi, 118; on falling bodies, ii, 53; on knowledge and perceptions, xvi, 87; on Mars, ii, 227; on origin of earth, xvi, 78; on shooting stars, ii, 283; scientific methods, xvi, 88-9; syllogism invention, 88; zoölogical work, 126 Arizona, arid topography, xiv, 42; cactus plants, xiii, 28, 106-7; chapparal of, xiv, 379; cliff lines of, 88; climate of plateau, 222; copper mines, iii, 360; faults at Bisbee, 90; forests of, xiv, 220-1, 373-4; Gila monster of, xii, 204, 207; mesas, xiv, 82; sunniest state, i, 86; timber limits, xiv, 373; volcanic fields of, 102, 315, 317, 318 Arkansas, aluminum production, iii, 369; hot springs of, xiv, 143, 144; malaria campaign in, x, 173-4 Arkwright, Richard, v, 274, 376 Armadillos, xii, 282, 283-4; scales of, xv, 220 Armature Reaction, vi, 190, vii, 145-6 Armatures of Dynamos, iv, 307, vi, 176, vii, 362; of direct current generators, vi, 178, 179-86; of alternators, 196, 197-8, 202, 205, 207, 210, 212-13 Armatures of Magnets, iv, 250, vi, 30 (fig.), vii, 362; uses of, iv, 291-2 Armatures of Motors, vi, 223, 224-5, 235-6 Armies, crowd psychology in, xi, 326-7; fatigue in retreat, 275 Armor, development of, xv, 220-1 Armored Cable Wiring, vii, 61-2, 362 Armor Fishes, iii, 281, 282, 284 Armorican Range, xiv, 96, 235 Armor Plate, making of, v, 323, 382 Arms, arteries of, ix, 196-7; bones of, 67-8, (fig.), 77, (fig.); bones, growth of, 58; equal length of, 169-70; freedom of movement of, 66; grasping organs, 82; length as yard measure, iv, 45; length in man and apes, xv, 57, 59; muscles of, ix, 76-7 Arnold of Villanova, x, 41 Aromatic Hydrocarbons, viii, 232-6, 374 Arrack, from coco palm, xv, 125; Indian, xiii, 213 Arrhenius, on Martian life, ii, 248 on osmotic pressure, xvi, 164; theory of life, xii, 9 Arrows, development, and use of, xv, 213-16; Indian, 196 (fig.) Arsenic, affinity strength, viii, 128; atomic weight and symbol, 383; in copper ore, vii, 320; ores of, viii, 198, 270; properties, 169; specific gravity, 384; tests for, 201, 287, 288 Art, primitive types of, xv, 110-21; science and, iv, 9