Circulation of Blood, ix, 195-200, 51 (diagram), x, 331, 337; discovery, ix, 192, x, 61, 63-6, 69, xvi, 106-7; discovery prepared by Vesalius, x, 51, 52; efficiency, climatic effects on, x, 238-9; former ideas of, 62-3, 65-6 Circumcision, among early Jews, x, 15; untransmitted, 230 Circumzenithal Arc, i, 178, 180, 181, 369 Circues, iii, 66, xiv, 58 Cirro-Cumulus Clouds, i, 100, 103, 298 Cirro-Stratus Clouds, i, 99-100, 103, 179 Cirrus Clouds, i, 97, 99, 103, 179; false, 102, 104, 372 Cirrus Haze, i, 100 Cities, aeroplanes to relieve congestion, i, 41-2; climate, 333; dependence on farms, vii, 221; importance of lighting, vi, 279-80; sewage disposal, viii, 324-9; sites, favorable to, xiv, 219; snow removal, i, 117, xiv, 140-1; transportation facilities, vii, 198; water supplies and purification, viii, 317-24; white ways of, vii, 339-41 Citric Acid, viii, 222, 223; formed by plants, 336; solubility, 112 Citrus fruits, acids of, viii, 223 Civet (oil), xii, 353 Civets, xii, 351, 352-3, 354 Civilization, American, xv, 12, 131-2, 203; arts and sciences in, iv, 9, 10; climate and, xiv, 344, 357-62, xv, 31, 123-7, 383, xvi, 141; clothing, shelter, and fire in, ix, 308-9, xv, 229; conditions necessary to, 127-32; development of, 3-4, 13-14, 28-31, 187-204; dominant human impulses in, 185, 383; earliest seats, xvi, 47; evolution in, xv, 382, 383-4; foresight and, 383; geographic factors, xiv, 10, 31, xv, 122-3, 128-39; government and, 380; historic and prehistoric periods, xv, 167, 322; influence of environment on, 122-39; labor and, 125-6; measured by timepieces, v, 57; medicine and, x, 31; moral laws and, xvi, 45, 47-8; natural laws and, xv, 47-8, 382-3; specialization in, 131-2, 203; stages of, 187-204; struggle to establish high associations, xi, 204; transportation and, v, 18; various machines and, 300 (see also Progress) Civilized Races, facial angle in, xv, 45; feet of, 60-1; jaws in, 43; monogamy of, 289, 290, 295; natural selection in, 47-8 Civil War, Appalachian mountaineers in, xiv, 243; captive balloons in, v, 225; improvement of weapons in, 362, 380; medical service in, x, 180; scurvy in, 265; Selfridge's periscope, v, 200; Virginia weather, i, 308, 338; western rivers in, xiv, 194 Clams, xii, 58-60, 66-7; shells of, iii, 272 Clam Shell Cove, Staffa, xiv, 130 Clans, formation of, xv, 362-3 Clarinet, iv, 234 Clark, Alvan, telescopes, ii, 106, 109, 143 Clarksburg, W. Va., deep well at, iii, 120 Clausius, xvi, 135 Clavichord, xv, 318 Claw Hammers, v, 25