Even in times of peace the sea exacts a dreadful toll of lives and property. Before the war the annual loss by shipwreck around the British Isles alone was estimated at forty-five million dollars. But the war, although it was frightfully destructive to shipping, may in the long run save more vessels than it sank; for it has given us sound-detectors which should remove the danger of collisions in foggy weather, and the wireless compass, which should keep ships from running off the course and on the rocks. And now, if salvage engineering develops as it should, the sea will be made to give up not only much of the wealth it swallowed during the war, but also many of the rich cargoes of gold and silver it has been hoarding since the days of the Spanish galleon. INDEX Air, fighting waves, 334 raising ship, on, 319 war in, 123 Airplane, ambulance, 146 armored, 139 artillery-spotting, 131 camera, 173 cartridges, 131 classes of work, 127 fighting among clouds, 137 flying boats, 144 gasolene tank, 130 giant, 132 hospital, 146 launching from ship, 303 Liberty motor, 142 scouting, 125 scouts, 128 speed of, 134 spotting, 177 training spotters, 180 wireless telephone, 194 See also Seaplane Ambulance airplane, 146 Armored diving-suit, 330 Arms and armor, 111 Artillery, hand, 23 Atmosphere, shooting beyond, 64 Audion, 185 Balloon, Blimp, 260 helium, 164 historical, 148 hydrogen, 150 Balloon, kite, 174 principles, 150 record flight, 65 Barbed wire, 15 cylinders, 17 gate, trench, 9 gates through, 15 shelling, 16 Barge for towing seaplanes, 302 Barrage, grenade, 27 mine, 292 Battle-fields, miniature, 180 Blimp, 260 Blisters on ships, 307 Boats, electric, 308 Eagle, 301 flying, 144 surface, 298 Bombs to destroy barbed wire, 16 Breakwater, pneumatic, 335 Browning, John M., 56 Buildings, shadowless, 227 Caisson disease, 325 Caliber, 68 Camera, airplane, 173 Camouflage and camoufleurs, 211 buildings, 227 grass, 229 horse, 223 land, 222 roads, 225 Camouflage, ships, 211 Cartridges, aircraft guns, 131 Catapults, 36 Caterpillar tractor, 109 Caves, 8 Coffer-dam, salvage, 318 Color, analyzing, 229 screens, 229 Compass, wireless, 201 Convoy, 267 Countermines, 17 Deep sea, conditions in, 312 Deep water diving, 327 Depth bombs, 265 Devil's eggs, 276 Diesel engine, 240 Direction-finder, 205 Dirigible, see Balloon Disease, caisson, 325 Diver, armored suit, 330 caisson disease, 325 rest chamber, 328 sled, 330 submarine torch, 329 suit, 324 Diving, deep, 324 record depth, 327 Duck-boards, 9 Dugouts, 7 Dummy heads of papier mâché, 13 Eagle boats, 301 Egg-laying submarines, 287 Eggs, Devil's, 276 Electric motor-boat, 308