=305. Barometers.= Barometers (Fig. 162) are devices which show changes in pressure and currents of air. Changes in the barometer usually indicate changes in the weather, and thus they are of interest to all persons. A decided fall in the mercury of a barometer usually precedes foul weather, while a rise indicates the approach of fair weather. When the pressure is low in any locality, air begins to rush toward that point as it would to fill a vacuum. So a fall in the barometer precedes the coming of a high wind or a rainstorm. A rise in the barometer precedes a calm, and since most rain is accompanied with wind, the calm is a time of fair weather. INDEX A Absorption of heat and light, 84, 85, 108 Acetylene, 30, 49, 81, 91, 92, 145, 221, 222, 223 Acids, 155, 156, 157, 159, 216 Acre, 229 Adjustment of burners, stove, 24, 29, 30, 32, 34, 41, 49, 78, 79, 80 Air, for circulation, 57, 76, 101, 102, 103, 111, 198 dead or stagnant, 63, 102 for combustion, 16, 29, 31, 38, 39, 48, 66, 88, 93, 214 for evaporation, 105, 176, 220, 221 for heating, 19, 55, 60, 61, 62, 63, 73, 75, 79 in radiator, 67, 68, 70 mixer, 23, 24, 25, 33, 77, 96, 144 moisture, 239 for pressure, 97, 112, 113, 114, 175, 176, 184 shaft, 57 whistling, 56 Alcohol, 47, 48, 89, 96, 97, 98, 145, 223 Alkalies, 155, 157 Alternating current, 110 Aluminum, 78, 156, 157, 158, 171, 172 Ammonia, 108, 138 Ampere, 82 Andiron, 74 Anthracite coal, 219 Asbestos, 32, 66, 77, 81 Ash chute, 22 Ashes, 20, 57, 66, 74, 75, 76 Automobile, 192 B Back-fire, 192, 214 Bacteria, 100, 101, 127 Balances, 225 Balling hydrometer, 238 Barometer, 239, 240 Barrel, 167, 228, 229 Basin, catch, 127 Battery, 192, 193, 194, 215, 216 Baume hydrometer, 237 Bearing, 152 Beater, 165 Bell for storing gases, 222 Bellows, 148, 149 Belts, 136, 137, 141, 186, 215 Bituminous coal, 219 Blau gas, 223 Bobbin, 187, 188, 189 Boiler, 64, 69, 71, 73, 132, 133, 156 Booster, 119 Bracket, curtain, 185 Brine for cooling, 108 British thermal unit, 218, 219 Brix hydrometer, 238 Broiler, 26 Brush, 147, 149, 150, 152 Bunsen burner, 77, 78, 81 Burner, 48, 96, 119, 141, 145, 198 gas, 23, 25, 27, 29, 77, 78, 88, 91, 144 kerosene, 32, 33, 36, 37, 40, 80, 94 Burning back, 27, 89, 90, 91 Burr grinder, 162 Bushel, 228, 229 C Calcium carbide, 221, 222, 223 Candle power, 84, 89, 91, 95 Canned heat, 48 Canner, 172, 173 Can sealer, 175 Capillary attraction, 47, 48, 93, 106 Carbolic acid, 126 Carbon, 82, 83, 84, 214 Carbon dioxide, 67, 108 Carburetor, 29, 192, 220 Carpet sweeper, 147, 148, 150 Cast aluminum, 156 Cast iron, 155, 156 Catch basin, 127 Centigrade thermometer, 233, 234 Centigram, 226 Centimeter, 228, 229 Centiliter, 228 Centrifugal dryer, 138, 139, 140 force, 139 washer, 135, 136