Black Forest, Germany, xiv, 238-9; geology of, 87 (map), 90, 117, 128 Black Hills, xiv, 93, 227; core of, 111; former forests of, 373; mineral springs of, 145 Black Hole of Calcutta, i, 321, ix, 268, x, 238 Black Lead, iii, 331, viii, 43 (see Graphite) Black Lightning, i, 148 Black Powder, viii, 144-5, 260 Black Race, xv, 32; brain and skull capacity, 41; disease immunity and susceptibility, 48-9, 50-1; facial angle in, 45; fitted to tropics, 50; jaw angle, 44; nose index and nostril shape, 46; peoples, 37; separate origin theory, 69, 70; skull shape, 42; type characters of, 35 Black Sea, hanging valleys on shore of, xiv, 58; importance of ports, 267; salinity of, 296, viii, 139; sturgeons of, xii, 152 Blacksnakes, xii, 218-19, 229 Blair, Henry, xvi, 187 Blanc, Mount, observatory on, ii, 142-9; "resurrection," i, 168; sound intensity on, 186 Blankets, warmth of, iv, 178 Blast Furnaces, v, 317-18; air blast of, viii, 158; ancient Egyptian, xvi, 74; carbon uses, viii, 157; cooling of air for, v, 347; development of modern, 315-16, xvi, 174, 175, 176; oxygen in, i, 33; potash from dust, viii, 279 Blasting, v, 261-2; explosives for, viii, 260; with compressed air, i, 27; with water, v, 100 Blasting Powders, viii, 137-8 Bleaching, chemistry of, viii, 86; chlorine, 85-6; hydrogen peroxide, 41, 86; ozone, vii, 354; sulphur dioxide, viii, 78, 146; of wool, 256 Bleaching Powder, viii, 86-7, 146, 153, 274 Bleeders, Bleeding Sickness, ix, 181; transmission of, x, 234 Bleeding, from arteries and veins, x, 39; leeches used for, xii, 55; stopping of, ix, 179-81 Blended Inheritance, ix, 334, x, 230-1; in animal and plant breeding, ix, 337 Blériot, flight of, i, 43 Blight, cause of, xiii, 71 Blind, optophone reading for, v, 332, 334-5, 384; space perception by, xi, 168-9 Blindness, black seen in, ix, 116; cause, xi, 96-7; from brain disease, ix, 146; from cataract, 112 Blind Spot, xi, 87-9 Blish, Commander, v, 367-8 Blizzards, i, 133-4, 368; device against, 345 Block and Tackle, v, 34-5 Block Mountains, iii, 138-9, xiv, 117, 226 Block Signal Systems, v, 211, vii, 355-9 Block Tin, viii, 161