vl INDEX TO 
Thermo-electricity, laws of, 182. 
Thermometer, the mercurial, 85; quadrant or 
metal, 88; Breguet’s, ib. ; air, 89; Rumtord’s 
differential, 104 ; Leslie’s differential, descrip- 
tion and engraving of, 105; Melloni’s thermo- 
multiplier, ib. ; Kinnersley’s, 149 ; self-regis- 
tering, 187. 
Thunder, different kinds of, 243; seasons and 
localities of thunder-storms, 246. 
Tones, formation of musical, 74; method of de- 
termining the number of vibrations in, 78; on 
the beats of, 81. 
Tongue, explanation of the term, 80; tongue- 
work, ib. 
Tornadoes, effects of, 203. 
Torricelli, the law of, respecting the efflux of 
liquids, 46 ; invention of the barometer, 50. 
Torricellian vacuum, the, 91. 
Torsion balance, the, of Coulomb, 
Turbines, 48. — 
Twilight, morning and evening, 227; duration 
of, 228. 
145. 
Undulatory theory of light, the, 131. 
Van Marum’s plate electrical machine, 151. 
Vapor, formation of, 91; elasticity or tension of, 
ib.; apparatus for determining its expansive 
force, 92; Gay Lussac’s method of ascertain- 
ing the density of watery, 93; may be con- 
densed by pressure and cold, 94; mixture of, 
with air, 95; variable amount of, in the atmo- 
sphere, 208; formation and condensation of, 
209. 
Vaporization, 95 ; experiments in, 96. 
Variation of the compass, 142. 
Velocity of efflux, 46, 67. 
Vibrations, of strings, transverse, 70 ; of plates, 
bells, &c., ib.; number of, in a tone, method 
of determining, 78; Lagrange’s propositions 
concerning, 79; longitudinal, ib.; strength- 
ened by resonance, 82. 
600 
PHYSICS. 
Vision, limit of distinct, 125 ; angle of, 126. 
Voice, organs of, 83. 
Volta’s straw and gold leaf electrometer, 147 ; 
theory of galvanism, 156 ; experiments, 157 ; 
the Voltaic pile, ib. and 160. 
Volumeter, the, of Kopp, 54. r 
Water, reaction and impact of, 47; wheels, 48 ; 
regulator, 67; its peculiarities of contraction 
and expansion, 89 ; from melting snow, 222. 
Water spouts, 205. 
Watt’s steam-engine, description of, 99. 
Wave motion in general, observations on, 69. 
Weathercocks, construction of, 196. 
Weber’s investigations upon the laws of magnet- 
ism, 143. 
Wedge, the, 8, 14. 
- Weight, 4. 
Wells’s theory of dew, 209. 
Wheatstone’s experiments to determine the velo- 
city of electricity, 155 ; telegraph, description 
of, 168. 
Wheel and axle, the, 8, 12. 
Whirl winds, 205. 
White’s pulley, 14. 
Wind-measurer, the, 67. 
Winds, theory of the, 196; velocity and strength 
of, 197, 198 ; regular and irregular or varia- 
ble, 198 ; the trade, 199 ; table of the direc- 
tions of, for various countries, 200 ; succession 
of, 201; influence of, on the barometer, ib. ; 
hurricanes, typhoons, and hot winds, 203 ; cold 
winds and whirlwinds, 205. 
Wollaston’s cryophorus, engraving of, 95; re- 
flecting goniometer, 112; camera lucida, 128 ; 
galvanic battery, 158. 
Zamboni’s dry pile, 160. 
Zodiacal light, the, 236; its true character ~ 
uncertain, 237. 
Zones, the torrid, temperate, and frigid, 186. 
