INDEX. 



451 



Syphon, action of, 1^ 

 Syringe, principle of, 1T6 



Tackle and fall, what is a, 105 

 Telegraph, atmospheric, ISl 

 Bain's, 4oO 

 chemical, 436 

 House's, 4:j6 

 Worse's magnetic^ 434 

 printing, 43G 

 Telegraphic method, the first proposed, 436 



wires, insulation of, 436 

 Telescope, equatorial, 303 

 reflecting, 365 

 refracting, 363 

 what is a, 363 

 Temperature, average, how found, 267 



greatest natural ever observ- 

 ed, -210 

 in winter and summer, differ- 

 ence between, 210 

 meaning of, SiW 

 varies with latitude, 367 

 Tenacity, what is, 26 

 Theory, physical, definition of a, 10 

 Thermometer, 233 



how graduated, 234 

 centigrade, 235 

 mercurial described, 234 

 Reaumur, described, 235 

 Thermometer-air, described, 236 

 Thermo-electricity, what is, 416 

 Thunder, cause of, 393 



storms, where most prevail, 394 

 Tides, origin of, 32 



Toes, advantage of tnming out in walk- 

 ing, 50 

 Tone in sound, 195 

 Tongueing, what is, 117 

 Tdrnadoes, how produced, 2S7 



what are. 2S7 

 Torpedo, electrical effects of, 391 

 Torricelli's invention, 109, 170 

 Trade winds, cause of. 2S3 



direction of, 2S3 

 Transparent bodies, 294 

 Troy weight, 34 

 Trumpet, ear, what is an, 200 



speaking, construction of, 199 

 Tubes, capillary, height to which water 



rises in, 143 

 Twilisht, 314 

 Twinkling, what is, 333 

 Tympanum of the ear, 203 



"Vacnnm, what is a, 168 

 Valve, definition of, 1S3 



safety, "258 

 Variation, lines of, 406 

 Vapor, always present in air, 239 



appearance of, 233 

 Vapors, elasticity of, 243 



formed at all temperatures, 233 

 Vault, what is a, 120 

 Velocity defined, 63 



Velocitv of moving bodv, how determined, 



63 

 Vena contracta, what is the, 150 

 Ventilation, what is, 200 



when perfect, 260 

 Vessels of liquid, pressure upon the bot- 

 tom of, 131 

 Vibrations of sound, nature of, ISS, 1S9 

 Views, dissolving, 363 

 Vision, angle of, 354 



deceptions of, 357 

 double, how produced, 354 

 phenomena of, 347 

 Vital action, 214 

 Voice, compass of, 200 



how produced, 203 

 organs of, 201 ^ 



Voltaic piles, 404 

 Volume defined, 12 



"Walls, how deafened, 192 

 Warming and ventilation, 260 

 Warp and woof. 117 

 Watch, how diff>'rs from a clock, 50 

 Water as a motive power, 155 

 boiled, why flat, ISO 

 boiling, temperature of, 241 

 composition of, 123 

 compressibility of, 124 

 decomposition of, 413 

 elasticity of, 124 

 expands in freezing, 231 

 force of expansion of in freezing, 239 

 freezing temperature of, 232 

 greatest capacity of all bodies for 



heat, 248 

 how high rises in a pump, 1S3 

 how made hot, 221 

 illustrations of the pressure of, 130 

 imparts no additional heat after boil- 

 ing, 244 

 inclination suflScient to give motion 



to, 152 

 level. 1.36 

 power defined. 83 

 pressure at different depths, 131 



how calculated, 133 

 sound of falling, how produced, 2(K 

 spouts, what are, 287 

 supply of towns, 134 

 to what degree can be heated, 249 

 velocity of in pipes, how retarded, 151 

 when has its greatest density, 231 

 why rises by suction, 109 

 why rises in a pump, 183 

 Waters, comparative purity of, 123 

 Wave, a form, not a thing, 153 

 Waves, height of, 153 



optical dclvisions of, 153 

 origin of, 153 

 of sound, 190 

 Weather, popular opinions concerning, 291 

 Wedge, what is a, lti6 



when used in the arts, 107 

 how tlie power of increases, 107 

 Weight, absolute, what is, 3S 



how determined by spe- 

 cific gravity, 43 



