Chapter 35
HOW ELECTRICITY IS OBTAINED ON A LARGE SCALE
318. The Dynamo. We have learned that cells furnish current as a result of chemical action, and that the substance usually consumed within the cell is zinc. Just as coal within the furnace furnishes heat, so zinc within the cell furnishes electricity. But zinc is a much more expensive fuel than coal or oil or gas, and to run a large motor by electricity produced in this way would be very much more expensive than to run the motor by water or steam. For weak and infrequent currents such as are used in the electric bell, only small quantities of zinc are needed, and the expense is small. But for the production of such powerful currents as are needed to drive trolley cars, elevators, and huge machinery, enormous quantities of zinc would be necessary and the cost would be prohibitive. It is safe to say that electricity would never have been used on a large scale if some less expensive and more convenient source than zinc had not been found.
319. A New Source of Electricity. It came to most of us as a surprise that an electric current has magnetic properties and transforms a coil into a veritable magnet. Perhaps it will not surprise us now to learn that a magnet in motion has electric properties and is, in fact, able to produce a current within a wire. This can be proved as follows:--
Attach a closely wound coil to a sensitive galvanometer (Fig. 237); naturally there is no deflection of the galvanometer needle, because there is no current in the wire. Now thrust a magnet into the coil. Immediately there is a deflection of the needle, which indicates that a current is flowing through the circuit. If the magnet is allowed to remain at rest within the coil, the needle returns to its zero position, showing that the current has ceased. Now let the magnet be withdrawn from the coil; the needle is deflected as before, but the deflection is in the opposite direction, showing that a current exists, but that it flows in the opposite direction. We learn, therefore, that a current may be induced in a coil by moving a magnet back and forth within the coil, but that a magnet at rest within the coil has no such influence.
An electric current transforms a coil into a magnet. A magnet in motion induces electricity within a coil; that is, causes a current to flow through the coil.
A magnet possesses lines of force, and as the magnet moves toward the coil it carries lines of force with it, and the coil is cut, so to speak, by these lines of force. As the magnet recedes from the coil, it carries lines of force away with it, this time reducing the number of the lines which cut the coil.
320. A Test of the Preceding Statement. We will test the statement that a magnet has electric properties by another experiment. Between the poles of a strong magnet suspend a movable coil which is connected with a sensitive galvanometer (Fig. 237). Starting with the coil in the position of Figure 228, when many lines of force pass through it, let the coil be rotated quickly until it reaches the position indicated in Figure 238, when no lines of force pass through it. During the motion of the coil, a strong deflection of the galvanometer is observed; but the deflection ceases as soon as the coil ceases to rotate. If, now, starting with the position of Figure 238, the coil is rotated forward to its starting point, a deflection occurs in the opposite direction, showing that a current is present, but that it flows in the opposite direction. So long as the coil is in motion, it is cut by a varying number of lines of force, and current is induced in the coil.
_The above arrangement is a dynamo in miniature_. By rotation of a coil (armature) within a magnetic field, that is, between the poles of a magnet, current is obtained.
In the _motor_, current produces motion. In the _dynamo_, motion produces current.
321. The Dynamo. As has been said, the arrangement of the preceding Section is a dynamo in miniature. Every dynamo, no matter how complex its structure and appearance, consists of a coil of wire which can rotate continuously between the poles of a strong magnet. The mechanical devices to insure easy rotation are similar in all respects to those previously described for the motor.
The current obtained from such a dynamo alternates in direction, flowing first in one direction and then in the opposite direction. Such alternating currents are unsatisfactory for many purposes, and to be of service are in many cases transformed into direct currents; that is, current which flows steadily in one direction. This is accomplished by the use of a commutator. In the construction of the motor, continuous _motion_ in one direction is obtained by the use of a commutator (Section 310); in the construction of a dynamo, continuous _current_ in one direction is obtained by the use of a similar device.
322. Powerful Dynamos. The power and efficiency of a dynamo are increased by employing the devices previously mentioned in connection with the motor. Electromagnets are used in place of simple magnets, and the armature, instead of being a simple coil, may be made up of many coils wound on soft iron. The speed with which the armature is rotated influences the strength of the induced current, and hence the armature is run at high speed.
A small dynamo, such as is used for lighting fifty incandescent lamps, has a horse power of about 33.5, and large dynamos are frequently as powerful as 7500 horse power.
323. The Telephone. When a magnet is at rest within a closed coil of wire, as in Section 319, current does not flow through the wire. But if a piece of iron is brought near the magnet, current is induced and flows through the wire; if the iron is withdrawn, current is again induced in the wire but flows in the opposite direction. As iron approaches and recedes from the magnet, current is induced in the wire surrounding the magnet. This is in brief the principle of the telephone. When one talks into a receiver, _L_, the voice throws into vibration a sensitive iron plate standing before an electromagnet. The back and forth motion of the iron plate induces current in the electromagnet _c_. The current thus induced makes itself evident at the opposite end of the line _M_, where by its magnetic attraction, it throws a second iron plate into vibrations. The vibrations of the second plate are similar to those produced in the first plate by the voice. The vibrations of the far plate thus reproduce the sounds uttered at the opposite end.
324. Cost of Electric Power. The water power of a stream depends upon the quantity of water and the force with which it flows. The electric power of a current depends upon the quantity of electricity and the force under which it flows. The unit of electric power is called the watt; it is the power furnished by a current of one ampere with a voltage of one volt.
One watt represents a very small amount of electric power, and for practical purposes a unit 1000 times as large is used, namely, the kilowatt. By experiment it has been found that one kilowatt is equivalent to about 1-1/3 horse power. Electric current is charged for by the watt hour. A current of one ampere, having a voltage of one volt, will furnish in the course of one hour one watt hour of energy. Energy for electric lighting is sold at the rate of about ten cents per kilowatt hour. For other purposes it is less expensive. The meters commonly used measure the amperes, volts, and time automatically, and register the electric power supplied in watt hours.
INDEX
Absorption, of heat by lampblack, 143-144. of gases by charcoal, 57. of light waves, 135-138.
Accommodation of the eye, 123.
Acetanilid, 259.
Acetylene, as illuminant, 152-153. manufacture of, 152-153. properties of, 220.
Acid, boric, 253. carbolic, 152, 251, 252. hydrochloric, 55, 80, 227, 238, 241. lactic, 230. oxalic, 247, 248. salicylic, 253. sulphuric, 55, 80, 240, 241, 307. sulphurous, 242.
Acids, action on litmus, 220.
Adenoids, 51.
Adulterants, detection of, 16.
Air, characteristics of, 81-83, 86, 189. compressibility of, 91. expansion of, 10-11. humidity, 38, 39. pumps, 201-205. transmits sound, 269. weight of, 86. _See_ Atmosphere.
Alcohol, 234. in patent medicines, 260.
Alizarin, 248.
Alkali, 222.
Alternating current, 351.
Alum, 247. in baking powder, 230.
Ammeter, 341, 343.
Ammonia, 152. a base, 221-222. in bath, 226. in manufacture of ice, 98. neutralizing chlorine, 240.
Ampere, 342.
Anemia, 259.
Angle, of incidence, 110. of reflection, 110. of refraction, 114.
Aniline, 152, 245.
Animal charcoal, 58.
Animal transportation, 132.
Antichlor, 240.
Antipyrin, 259.
Armature, 319, 320. dynamo, 350. motor, 335.
Artificial lighting, 148-153.
Atmosphere, 81. carbon dioxide in, 54-55. height of, 81. nitrogen and oxygen in, 262. pressure of, 82-86. water vapor in, 36-38. weight, 86. _See_ Air.
Atmospheric pressure, 82-86.
Atomizer, 92.
Atoms, 102.
Automobiles, gas engines, 185.
Axis of a lens, 119.
Bacteria, 133. as nitrogen makers, 263. destroyed by sunlight, etc., 133, 250, 251. diseases caused by, 133. in butter and cheese, 133.
Baking powder, 229-230.
Baking soda, 227-229.
Barograph, 87.
Barometer, aneroid, 84-85. mercury, 84. use in weather predictions, 86-87.
Bases, action on litmus, 221-222. properties, 220-222.
Battery, electric, 311.
Beans, as food, 66. roots take in nitrogen, 263.
Bell, electric, 319-321.
Benzine, 150. as a cleaning agent, 227.
Benzoate of soda, 253.
Bicarbonate of soda, in fire extinguisher, 55, 56. in Rochelle salt, 227. in soda mints, 231. in seidlitz powder, 231.
Bicycle pumps, 202.
Blasting, by electricity, 314.
Bleaching, 237-243. by chlorine, 238-240.
Bleaching powder, 239-240.
Body, human, 63-64. a conductor of electricity, 292.
Boiling, 31. amount of heat absorbed, 31-32. of milk, 32. of water, 77. point, 15.
Bomb calorimeter, 61.
Borax, as meat preservative, 253. as washing powder, 226.
Boric acid, as meat preservative, 253.
Boyle's law, 95-96.
Bread, 232-233. unleavened, 233.
Bread making, 232-235.
Breathing, hygienic habits of, 50. by mouth, 50-51.
Burns, treatment of, 52-53.
Butter, adulteration test, 16. bacteria in, 133.
Buttermilk, 230.
Caisson, 203-204.
Calcium carbide, 152-153. in making nitrogenous fertilizer, 264.
Calico printing, 249.
Calorie, 27-28, 61-62.
Calorimeter, 61.
Camera, 128-129. films, 129. lens, 129. plates, 129.
Camping, water supply, 195-197.
Candle, 148-149. as standard for light-measure, 104-105.
Candle-power, 105-107.
Carbide, calcium, 152-153, 264.
Carbohydrates, 64-65, 149.
Carbolic acid, 152. as disinfectant, 251.
Carbon, 56, 66. in voltaic cells, 308.
Carbon dioxide, 53. as fire extinguisher, 55-56. commercial use, 55-56. in baking soda, 228. in fermentation, 234. in health, 54. in plants, 55. preparation of, 55. source of, 53. test for, 228.
Catarrh, 259.
Caustic lime, 222..
Caustic potash, 222.
Caustic soda, 218, 222. to make a salt, 227.
Caves and caverns, 71.
Cell, dry, 310. gravity, 309-310. voltaic, 306-308, 310.
Cells of human body, 63, 64, 66.
Centigrade thermometer, 15.
Central heating plant, 19.
Chalk, in making carbon dioxide, 55.
Charcoal as a filter, 57. commercially, 57. preparation, 57-58.
Chemical action, and electricity, 307, 315-317. and light, 126, 127.
Chemistry, in daily life, 218, 219.
Chills, 38.
Chloride of lime, in bleaching, 240. disinfectant, 251.
Chlorine, and hydrogen, 239. effect upon human body, 239. in bleaching, 238-240. influence of light upon, 126. presence in salt, 227.
Circuit, electric, 321. local, in telegraph, 325-326.
City water supply, 206-212.
Clarinet, 297.
Cleaning of material, 226, 243.
Climate, influenced by presence of water, 29, 40.
Clover, nitrogen producers, 263.
Coal, 30.
Coal gas, 150, 151. by-products, 152.
Coal oil, 149, 150.
Coal tar dyes, 152, 218, 245.
Cogwheels, 170.
Coil, current-bearing, 320. magnetic field about, 331-333.
Coke, 152.
Cold storage, 97.
Color, 134-141. and heat, 142, 143. influenced by light, 137. of opaque bodies, 136, 137. of transparent bodies, 135, 136.
Color blindness, 140, 141. designs in cloth, 248, 249.
Colors, compound, 138, 139. essential, 139-140. primary, 135. simple, 138. spectrum, 134-135. variety in dyeing, 247, 248.
Combustion, heat of, 45. spontaneous, 52.
Commutator, 335.
Compass, 328.
Compound colors, 138, 139.
Compound machine, 171.
Compound substances, 103.
Compression of air, 91, 92. cause of heat, 96.
Compression pumps, 201, 205.
Concave lens, 118.
Condensation, 33. heat set free, 40.
Conduction of heat, 25.
Conductivity metals, 321.
Conductors, electric, 321, 322.
Conservation, of energy, 58, 59. of matter, 58, 59.
Convection, 24, 25.
Convex lens, 118.
Cooling, by evaporation, 35-36. by expansion, 97.
Copper, in electric cell, 307.
Core, iron, 319.
Corn, bleached with sulphurous acid, 242.
Cotton, mercerized, 218. bleaching, 241. dyeing, 245-247.
Cough sirup, 258.
Crane, compound machine, 172.
Cream of tartar, 229.
Creosote oil, 254.
Crude petroleum, 149, 150.
Current, electric, 306, 312. alternating, 349. induced, 346-347. measurement of, 340. resistance, 312, 343, 345. strength, 339, 340, 344.
Dams, 214-216.
Decay, 49.
Decomposition of soil by water, 70-74.
Degrees Fahrenheit and Centigrade, 15.
Density, 11.
Designs in cloth, printed, 248, 249. woven, 249.
Developer in photography, 128.
Dew, 36, 37.
Dew point, 38.
Diarrhea, 251.
Diet, 62, 66. economy on table, 66-69.
Discord, reason for, 271.
Disease, and surface water, 76. relation of light to, 131-132.
Disease disinfectants, 250, 251, 252.
Distillation, 34-35. in commerce, 35. of petroleum, 149-150. of soft coal, 150. of water, 34, 35, 77.
Diving suits, 204.
Door bells, 319-321.
Drainage, of land, 194, 195. sewage, 196, 198, 199, 201.
Drilled well, 199.
Drinking water, 75-77. in camping, 195-196. and rural supplies, 198, 201.
Driven well, 196-197.
Drought, 217.
Drugs, 255, 260.
Dry cell, 312.
Dyeing, 244-249. color designs, 248.
Dyeing, direct, 245. home, 247. indirect, 247. variety of color, 247.
Dyes, 218, 244, 245.
Dynamo, 346. alternating current, 349. source of energy, 346-347.
Ear, in man, 301-303. care of, 303.
Earth, conductor of electricity, 326.
Echo, 277.
Economy in buying food, 66-69.
Effort, muscular, 155, 160.
Electric, battery, 311. bell, 319-321. bread toasters, 314. conductors and non-conductors, 321-322. cost of, energy, 352. current, 306, 312. flatiron, 313. heating pad, 314. lights, 314. street cars, 337.
Electricity, heat, 312-315, 339. as a magnet, 319, 331-333. practical uses of, 312-317.
Electrodes, of cell, 308.
Electrolytic metals, 317.
Electromagnets, 319.
Electromotive force, 308. unit of, 344.
Electroplating, 315.
Electrotyping, 317.
Elements, 102-103.
Emulsion, 224.
Energy, conservation of, 58, 59. transformations of, 58, 59.
Engine, steam, 183-185. gas, 185-186. horse power, 173.
Erosion, 73-74.
Essential colors, 139-140.
Evaporation, 35-39. cooling effect, 35-36. effect of temperature on, 35, 36. effect of air on, 38. freezing by, 98. heat absorbed, 36. of perspiration, 38.
Expansion, of air, 10, 11. cooling effect of, 97. disadvantage and advantage of, 11-13. of liquids, 9-11. of solids, 10, 11. of water, 9, 10, 11, 12. Eye, 122-125. headache, 124, 125. how focused, 122, 123. nearsighted and farsighted, 123. strain, 125.
Fahrenheit thermometer, 15.
Fats, 65. in soap making, 223.
Fermentation, 232-236. by yeast, 234-236.
Ferric compounds, 248.
Fertilizers, 262-265. nitrogen, 262. phosphorus, 263, 264. potash, 263-265.
Field magnet, 336.
Filings, iron, 329.
Film, photographic, 129.
Filter, charcoal, 57.
Filtering water, 77.
Fire, 9. and oxygen, 45, 47. and tinder box, 47. making of, 51. primitive production of, 47. produced by friction, 47. spontaneous combustion, 52. sores and burns, 52-53. extinguisher, 55, 56.
Fireless cooker, 25, 26.
Fireplaces, 17, 18.
Fixing, in photography, 128.
Flame, hydrogen, 80.
Flood, Johnstown, 214, 215. relation to forests, 217.
Flour, self-raising, 231.
Flume, 177.
Flute, 297.
Focal length, 118.
Focus, of lens, 118.
Fog, 37.
Food, 60-69. carbohydrates, 64, 65. economy in buying, 66-69. fats, 65. fuel value of, 60-62. need of, 63, 64. preservatives, 252. proteids, 66. value, 67. waste, 60. water in, 75.
Foot pound, 172.
Force and motion, 156, 157. and work, 156, 157. magnetic lines of, 329-331, 334. muscular, 155, 160.
Force pumps, 192, 193.
Forests and water supply, 216-217.
Forging of iron, 40, 41.
Formaldehyde, 253.
Freezing, effect of salt, 44. effect on ground and rocks, 42. expansion of water on, 41. ice cream freezer, 44.
Frequency in music, 273, 275.
Fresh air, 22-24, 49. amount consumed by gas burner, 22. and health, 49, 50. in underground work, 202. in work under water, 203-205.
Friction, 173, 174. losses by, 174, 210. source of heat and fire, 47.
Frost, 36, 37.
Fruit, canned, bleached with sulphurous acid, 242. colored with coal tar dyes, 253.
Fuel value of foods, 60-62. table of fuel values, 67.
Fulcrum, 159, 160.
Fumigation, 251.
Fundamental tone, 290, 291, 292.
Furnace, hot air, 19.
Fuse, 340.
Fusion, heat of, 40.
Galvanometer, 341.
Gas, acetylene, 152, 153. and unburned carbon, 151. coal, 151, 152. effect of heat on volume, 96, 97. effect of pressure on volume, 95-96. engine, 185-186. for cooking, 151, 152. illuminating, 92, 93, 150, 151. liquefaction, 97, 98. meter, 93, 94. natural, 152.
Gasolene, 149, 150. as cleaning agent, 227, 243. in gas engine, 185, 186.
Gauge, pressure, 92-94.
Gelatin, plate and film, 129.
Glass, kinds of, 119. molding of, 40. non-conductor, 321.
Grape juice, fermented with millet, 233.
Gravity cell, 309, 310.
Grease, and lye, 221. and soap making, 223.
Gulf Stream, 24.
Hard water, and soap, 225.
Harp, 295.
Headache, 124, 125. powders, 259.
Health, effect of diet, 62, 64.
Heat, 9. absorbed in boiling, 31-32. and disease germs, 250. and food, 252. and friction, 47. and light, 142, 147. and oxidation, 45, 48, 49. and wave motion, 145-147. conduction, 25. convection, 24, 25. from burning hydrogen, 80. from electricity, 312-315, 339. needed to melt substances, 39. of fusion, 40. of vaporization, 32. produced by compression, 96. relation of water to weather, 29, 40. set free by freezing water, 40. sources of, 29-30. specific, 28-29. temperature, 27. unit of, 27, 28.
Heating effect of electric current, 312-315.
Heating of buildings: central heating plant, 19. fireplaces, 17-18.
Heating, furnaces, 19. hot water, 19-22.
Helix, 318.
Horse power, 173, 351.
Hot water heating, 19-22.
Hues, primary, 135.
Humidity, 38. proper percentage for health and comfort, 38, 39.
Humus, 216, 217.
Hydrocarbons, 149.
Hydrochloric acid, composition, 227. in bleaching, 241. to make a salt, 227. to make carbon dioxide, 55. to make chlorine, 238. to make hydrogen, 80.
Hydrogen, 65, 66. and chlorine, 239. and water, 79. chemical conduct, 126-127. flame, 80. in voltaic cell, 307. peroxide, 53, 252. preparation, 80. to liquefy, 97.
Ice, lighter than water, 42. manufacture of, 98, 99.
Ice cream freezers, 44.
Illuminating gas, manufacture of, 150, 151. measurement of quantity consumed, 93, 94. test of pressure, 92, 93.
Illumination, intensity of, 105, 106.
Image, in mirror, 108, 111.
Incandescent lighting, 107, 314.
Incidence, angle of, 110.
Inclined plane, 162-166. screw, 166. wedge, 166.
Indigo, 218.
Induced current, 346-347.
Ink spots, removal of, 243.
Insoluble substances, 71.
Insulators, electric, 324.
Intensity, of light, 105-107. of sound, 270-271.
Interval, in musical scale, 283.
Iron, forging, 41. filings, 329. galvanizing, 49. oxidation of, 48.
Irrigation, 193-194.
Isobaric lines, 88, 91.
Isothermal lines, 89, 91.
Johnstown flood, 214, 215.
Kerosene, 149, 150.
Kilowatt, 351.
Lactic acid, 230.
Leaves, 132, 262.
Lens, 117-121. concave, 118. converging, 118. crystalline, of eye, 122. focal length, 118. material, 119. refractive power, 119.
Lever, 158-162. examples, 160-162. fulcrum, 159, 160.
Life, and carbon dioxide, 54. and nitrogen, 261. and oxygen, 49, 54.
Lifting pumps, 189-192.
Light, absorption, 135-138. and heat, 142-147. a wave motion, 145-147. bent rays, 113, 114. chemical action, 126-127. disease, 131-132. essential to life, 131, 132. fading illumination, 105, 106. influence on color, 134. reflection of, 109-112. refraction of, 113-125. travels in a straight line, 108. white, composed of colors, 134.
Lighting, artificial, 148-153.
Lime, chloride of, 240, 251.
Limewater, 220. and carbon dioxide, 228.
Linen, bleaching, 241. dyeing, 245-247.
Lines, of force, 329-331, 334. isobaric, 88, 91. isothermal, 89, 91.
Liquefaction of gases, 97, 98.
Liquid air, 98.
Liquid soap, 223, 224.
Litmus, action of acids, 220. action of bases, 221, 222. action of neutral substance, 222.
Logwood dyes, 245, 247, 248.
Los Angeles aqueduct, 211.
Lye, 221, 222.
Machines, compound, 171. inclined plane, 162-166. lever, 158-162. pulley, 166-169. wheel and axle, 169-171.
Madder, for dyes, 245.
Magnet, 328. electro-, 319. field of, 329-331. lines of force about, 329-331. poles of, 330-332. properties of electricity, 318.
Magnetic, needle, 328. poles, 329-331.
Magnifying power, of a lens, 115. of a microscope, 115. of a telescope, 115.
Mammoth Cave of Kentucky, 71.
Manganese dioxide, 46. chlorine made from, 238. oxygen made from, 46.
Marble, for carbon dioxide, 55.
Matches, 47. safety, 47-48.
Matching colors, 137.
Matter, conservation of, 58, 59.
Meat, 66. preservation of, 253.
Mechanical devices, 154, 155.
Melting, 39, 40.
Melting point, 40.
Melting substances without a definite melting point, 40.
Mercerized cotton, 218.
Mercury, barometer, 84. thermometer, 14-17.
Metals, electroplating, 317. preservation by paint, 253-254. veins deposited by precipitation, 72, 73. welding, 315.
Meter, gas, 93, 94.
Microörganisms, 132, 133.
Microscope, 115.
Milk, boiling point, 32. Pasteurized, 250.
Minerals, in foods, 62, 63. in water, 70, 71.
Mirrors, 108-112. distance of image behind mirror, 111. distance of object in front of mirror, 111. image a duplicate of object. 111.
Molding of glass, 40.
Molecule, 100-103.
Mordants, 247, 248, 249.
Morphine, 257.
Morse, telegraphic code, 324.
Motion, in sound, 266, 278, 280. in work, 156.
Motor, electric, 336. principle of, 333. street car, 337.
Mouth breathing, 50. cause of, 51.
Movable pulley, 167, 168.
Music, 278.
Musical instruments, percussion, 299. stringed, 284-295. wind, 295, 299.
Musical scale, 282.
Naphtha in gas engines, 185.
Naphthalene, 152.
Narcotics, 255.
Natural gas, 152.
Needle, magnetic, 328.
Negative, electrode, 308. photographic, 130.
Neutral substance, 222. and litmus, 222.
Neutralization, 222.
Niagara Falls, 176.
Nitrogen, 66. and bacteria, 263. and plant life, 261. in atmosphere, 261. in fertilizer, 262-265. in food, 66. preparation of, 261. properties of, 261.
Noise in music, 280.
Non-conductors, of electricity, 321-322. of heat, 25.
Nutcracker, as a lever, 162.
Oboe, 297.
Octave, 284.
Odors, 101.
Ohm, unit of resistance, 345.
Oil, gasoline, 149, 150. kerosene, 149, 150. lubricating, 174. olive, 16.
Orchestra grouping, 299.
Ore, 72.
Organ pipes, 297.
Overtones, 290-293.
Oxalic acid, 247, 248.
Oxidation, 45-59. and decay, 49. heat the result of, 49-52. in human body, 49, 53. of iron, 48.
Oxygen, 66. and bleaching, 239. and combustion, 45. and food, 66. and plants, 55. and the human body, 50. and water, 79, 80. in the atmosphere, 45. preparation of, 46.
Paint, as wood and metal preservatives, 253, 254. removal of stains, 243.
Paper making, 219.
Paraffin, 150, 321.
Pasteurized milk, 250.
Patent medicines, 257-260.
Peas, sources of nitrogen, 263.
Pelton wheel, 177.
Percussion instruments, 299.
Period of a body, 273.
Peroxide of hydrogen, 53, 252
Petrolatum, 150.
Petroleum, 149, 150.
Phonograph, 303-305.
Phosphorus, in fertilizer, 263, 264. in making nitrogen, 261. in matches, 47, 48. poisoning by, 47.
Photography, 127-131.
Photometer, 107.
Pianos, 284-292.
Pin wheel, 181.
Pitch of sound, 280, 281. cause of, 282. in wind instruments, 296-299.
Plane, inclined, 162-166.
Plants, and atmosphere, 55. and light, 131-132. and nitrogen, 261.
Plate developing, photographic, 128.
Pneumatic dispatch tube, 205.
Poles, magnetic, 330-332. of cell, 308.
Positive electrode, 308.
Potash, in fertilizer, 263-265.
Potassium chlorate and oxygen, 46. permanganate, 100. tartrate and Rochelle salt, 227.
Power, candle, 105-107. electric, 351. horse, 173, 351. sources of, 174, 175, 185. transmission by belts, 171. water, 176-180.
Precipitation, 72, 73.
Preservatives, food, 252. wood and metal, 253-254.
Pressure, atmospheric, 82-86. calculation of atmospheric, 83, 84. calculation of gas, 92, 93. calculation of water, 94. gauge, 92-94. of illuminating gas, 93. relation of pressure of gas to volume, 95, 96. water pressure, 208-211, 214-216. within the body, 86.
Primary colors, 135.
Print, photographic, 131.
Printing, color designs in cloth, 248, 249. electrotype, 317.
Prisms, 135. refraction through, 117.
Proteids, 66.
Pulleys, 166-169. applications of, 169.
Pump, 187-205. air, 201-205. force, 192, 193. lifting, 189-192.
Pupil of the eye, 122.
Pure food laws, bleaching, 242. preservatives, 252.
Purification of water, 77, 196.
Push button, 321.
Radiator, 19-21.
Railroads, grading of, 165-166.
Rain, 36, 37.
Rainbow, 134.
Rain water, 225.
Reflection, angle of, 110. of light, 109-112. of sound, 278, 279.
Refraction, angle of, 114. by atmosphere, 114. of light, 113. uses of, 115-116.
Relay, telegraph, 325.
Reservoir, 214. artificial, 211. construction of, 214-216. natural, 211.
Resistance, electrical, 312. internal, of cell, 343. unit of, 345.
Resonance, 276.
River, volume and value of, 180.
Roads, application of inclined plane to, 165-166.
Rochelle salt, 227, 231.
Rocks, effect of freezing water on, 42-43. water as a solvent, 71.
Rosin, obtained by distillation, 35.
Safety matches, 47-48.
Salicylic acid, 253.
Salt, 227-228.
Salts, 227. general properties, 227. in ocean, 227. smelling, 222.
Saturation of air, 37.
Scale, musical, 282.
Screw, and inclined plane, 166.
Seaweed, 265.
Seidlitz powder, 231.
Self-raising flour, 231.
Sewage, disposition of, 198-199. of camps, 196. source of revenue, 201.
Sewer gas, 57.
Silk, bleaching, 241. dyeing, 245-247.
Silver chloride, 127-131.
Simple colors, 138.
Simple substances, 103.
Siren, 280.
Smelling salts, 222.
Snow, 36-37.
Soap, 222-224. and hard water, 225. liquid, 223-224. preparation, 223.
Soda, baking, 227, 228-229. benzoate, 253. caustic, 218, 222, 223, 227. washing, 225, 226, 229.
Soda mints, 231.
Sodium, bicarbonate, 56, 227, 228, 230-231. carbonate, 228. chloride, 228.
Soil, deposited by streams, 73.
Solenoid, 318.
Solution, 70.
Soothing sirup, 258.
Sound, and motion, 266, 278. musical, 278. nature of, 266. reflection, 277. speed of, 271-272. transmission of, 267-271. velocity of, 271-272. waves, 272-274.
Sounder, telegraph, 324.
Sounding board, 277.
Sour milk in cooking, 230.
Specific heat, 28-29.
Spectrum, 134-135.
Speed, of sound, 271, 272.
Spontaneous combustion, 52.
Stains, removal of, 226, 243.
Standpipes, 212.
Starch, 65.
Steam, and work, 183-184. engine, 183-185. heat of vaporization, 32. heating by, 33. turbine, 183-184.
Steel, forging and annealing, 16.
Stoves, 18-19.
Streams, carriers of mud, 73. volume of, 179-180.
Street cars, electric, 337.
Stringed instruments, 284-295.
Strings, vibrating, 286-290.
Sugar, 16, 65. fermented by yeast, 234.
Sulphur, 66. as disinfectant, 251. in making sulphurous acid, 242.
Sulphuric acid, in bleaching, 240,241. in fire extinguisher, 55. in making of hydrogen, 80. in voltaic cell, 307.
Sulphurous acid, in bleaching, 242. preparation, 242.
Sun, energy derived from, 143-144. source of heat, 29-30.
Sunlight, 135. and bacteria, 133. and chemical action, 126-127.
Sympathetic vibrations, 274-277.
Tallow, 105, 148.
Tartar, cream of, 229.
Telegraph, 322. long distance, 327. relay, 325. sounder, 324.
Telephone, 350-351.
Temperature, 13-14. as measurement of heat present, 27. in detecting adulterants, 17. in forging steel, 16. in making sirups, 16. measurement of, 14-15.
Thermometer, 14-17. Centigrade, 15. Fahrenheit, 15.
Tinder box, 47.
Transmission, of light, 145-147. of sound, 267-271.
Tuning fork, 266, 273, 278, 290.
Turbine, steam, 183. water, 178.
Turpentine, and grease, 226. by distillation, 35.
Unleavened bread, 233.
Vacuum, sound in, 268.
Vapor, in atmosphere, 36-38.
Vaporization, heat of, 32.
Varnish, on candies, 253.
Vegetable matter, and coal, 30. and gas, 30. and oil, 30.
Veins, formation in rock, 72-73.
Velocity, of sound, 271-272.
Ventilation, 21-24, 54. need of, 38.
Vibration, of strings, 286-290. sympathetic, 274-277.
Viola, 295.
Violin, 295.
Violoncello, 295.
Vocal cords, 300.
Voice, 300.
Volt, 344.
Voltage, 345.
Voltaic cell, 306-308, 310.
Voltmeter, 344.
Volume, of a stream, 179-180. relation of pressure of a gas, 95-96.
Washing powders, 224-226. soda, 229.
Water, action in nature, 70-74. amount used daily per person, 181. and hydrogen, 79. and oxygen, 79, 80. as solvent, 70-71. boiling, 77. boiling point, 15. composition, 79-80. condensation, 33. dams and reservoirs, 214-216. density, 11. distilled, 34, 77. drinking, 75-77, 195-201. electrolysis, 79-80. evaporation, 33-34. expansion, 9-10, 41-42. filtration, 77. freezing, 40-41. hard, 225. heat of fusion, 40. impurities, 76-77. in atmosphere, 36-38. in food, 75. in human body, 75. in vegetables, 75. influence on climate, 29, 40. irrigation, 193-194. minerals in, 70-71. ocean, 265. power, 176-180. precipitates, 72, 73. pressure, 208-211, 214-216. purification, 77. rain, 225. running, value of, 178-180. source of, 78. steam, 32. waves, 145-147. weight, 208-209, 215. wells, 195-201. wheels, 176-180. work under, 203-205.
Water supply, and forests, 216-217. cost, 212-214. of city, 206-212, 217.
Watt, 351.
Waves, heat, 145-147. light, 145-147. sound, 268, 272-274. water, 145-147.
Weather, bureau, 87-91. forecasts, 38-39, 86-88. relation of water to, 29, 40.
Weather maps, 89-91.
Wedge, and inclined plane, 166.
Weight, of air, 86. of water, 208-209, 215.
Welding, by electricity, 315.
Wells, 195-201. drilled, 199. driven, 196-197.
Wheel and axle, 169-171. cogwheels, 170. windlass, 169.
Wheelbarrow as lever, 160-161.
White light, nature of, 135.
Wind instruments, 297-301.
Windlass, 169.
Windmill, 174-175, 180-182.
Winds, 24.
Wine, 232, 234.
Wood, as source of charcoal, 58. ashes in soap making, 223. in paper making, 219. preservation, 253-254.
Wool, bleaching, 241. dyeing, 245-247.
Work, 156-186. and steam, 183-184. and water, 176-180. conservation, 174-175. formula, 157. machines, 157-175. unit of, 172-173. waste, 173.
Woven designs in cloth, 249.
Yeast, 234-236. wild, 235-236.
Zinc, in galvanizing iron, 49. in making hydrogen, 80. in voltaic cell, 307-308.
PLANT LIFE AND PLANT USES
By JOHN GAYLORD COULTER, Ph. D.
$1.20
An elementary textbook providing a foundation for the study of agriculture, domestic science, or college botany. But it is more than a textbook on botany--it is a book about the fundamentals of plant life and about the relations between plants and man. It presents as fully as is desirable for required courses in high schools those large facts about plants which form the present basis of the science of botany. Yet the treatment has in view preparation for life in general, and not preparation for any particular kind of calling.
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A NEW ASTRONOMY, $1.30
By DAVID TODD, M. A., Ph. D., Professor of Astronomy and Navigation and Director of the Observatory, Amherst College.
Astronomy is here presented as preeminently a science of observation. More of thinking than of memorizing is required in its study, and greater emphasis is laid on the physical than on the mathematical aspects of the science. As in physics and chemistry, the fundamental principles are connected with tangible, familiar objects, and the student is shown how he can readily make apparatus to illustrate them. In order to secure the fullest educational value, astronomy is regarded as an inter-related series of philosophic principles.
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MATHEMATICAL GEOGRAPHY, $1.00
By WILLIS E. JOHNSON, Ph. D., Vice-President and Professor of Geography and Social Sciences, Northern Normal and Industrial School, Aberdeen, South Dakota.
This work explains with great clearness and thoroughness that portion of the subject which not only is most difficult to understand, but also underlies and gives meaning to all geographical knowledge. A vast number of facts which are much inquired about, but little known, are taken up and explained. Simple formulas are given so that a student unacquainted with geometry or trigonometry may calculate the heights and distances of objects, the latitude and longitude of a place, the amount any body is lightened by the centrifugal force due to rotation, the deviation of a plumb-line from a true vertical, etc.
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ELEMENTS OF GEOLOGY
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An introductory course in geology, complete enough for college classes, yet simple enough for high school pupils. The text is explanatory, seldom merely descriptive, and the student gains a knowledge not only of the salient facts in the history of the earth, but also of the methods by which those facts have been determined. The style is simple and direct. Few technical terms are used. The book is exceedingly teachable.
The volume is divided into two parts, physical geology and historical geology. It differs more or less from its predecessors in the emphasis on different topics and in the arrangement of its material. Factors of minor importance in the development of the earth, such as earthquakes, volcanoes, and geysers, are treated much more briefly than is customary. This has given space for the extended discussion of matters of greater significance. For the first time an adequate discussion of the leading modern conceptions concerning the origin and early development of the earth is presented in an elementary textbook.
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ESSENTIALS OF BIOLOGY
By GEORGE WILLIAM HUNTER, A. M., Head of Department of Biology, De Witt Clinton High School, New York City.
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This new first-year course treats the subject of biology as a whole, and meets the requirements of the leading colleges and associations of science teachers. Instead of discussing plants, animals, and man as separate forms of living organisms, it treats of fife in a comprehensive manner, and particularly in its relations to the progress of humanity. Each main topic is introduced by a problem, which the pupil is to solve by actual laboratory work. The text that follows explains and illustrates the meaning of each problem. The work throughout aims to have a human interest and a practical value, and to provide the simplest and most easily comprehended method of demonstration. At the end of each chapter are lists of references to both elementary and advanced books for collateral reading.
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In this Manual the 56 important problems of Hunter's Essentials of Biology are solved; that is, the principles of biology are developed from the laboratory standpoint. It is a teacher's detailed directions put into print. It states the problems, and then tells what materials and apparatus are necessary and how they are to be used, how to avoid mistakes, and how to get at the facts when they are found. Following each problem and its solution is a full list of references to other books.
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ESSENTIALS OF PHYSICS
By GEORGE A. HOADLEY, C.E., Sc. D., Professor of Physics, Swarthmore College.
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This is the author's popular and successful Elements of Physics enriched and brought up to date. Despite the many changes and modifications made in this new edition, it retains the qualities which have secured so great a success for the previous book.
It tells only what everyone should know, and it does this in a straightforward, concise, and interesting manner. It takes into consideration the character of high school needs and conditions, and, throughout, lays particular emphasis upon the intimate relation between physics and everyday life.
While the subject matter, as a whole, is unchanged, the order of topics in many cases has been altered to adapt the development of the subject to the habits of thought of high school pupils. Instead of beginning the treatment of a subject with the definition and proceeding to a discussion of the sub-topics, the author starts with a discussion of well-known phenomena and leads up to the definition of the subject discussed. The text, wherever possible, has been simplified, more than fifty topics having been amplified, expanded, or reworded. More familiar illustrations of the topics treated are given, and the demonstrations of many of the experiments are simplified by the use of materials that are readily obtainable in the classroom.
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