IMDKX. 



Varieties of mankind, 270. 

 Vegetation, 262. 

 Velocity of light, 31. 



of electricity, 284. 



, comparative, 369. 



of the gravitating force, 386. 



Venus, her action on the earth, 25. 



, her nodes, 13, 52. 



, transit of, 52. 



, climate of, 240. 



Vibrations of musical strings, 134. 



of columns of air in pipes, 137. 



of elastic solids, 138 et seq. 



sympathetic, 1, 142. 



of polarized light, 176. Note 201. 



Volcanic action, 246. 



, theories of, 249. 



Volta, Professor, his construction of 



the Voltaic pile, 290. 

 Volta-electric induction, 323. 

 Voltaic battery, 292. 

 electricity, discovery of, 290. 



properties of, 294. 



luminous effects of, 295. 



chemical effects of, 296. 



transference of, 297. 



composition by, 297. 



effects of, on the senses, 299. 



Volume, 56. 



W. 



Water, decomposition and compo- 

 sition of, 296, 328, 336. 



of crystiilization, 105. 



a conductor of sound, 129. 



, rotation of, 316. 



Week, the antiquity of, 80. 



Weigh! of the atmosphere, 112. 



decreases from the poles to the 



equator, 44, 49. 



Weight at the surfaces of the sun 

 and planets, 56. 



Weights and measures, 84. 



Wheatstone, Professor, his musical 

 instruments, 138. His experiments 

 on vibrating surfaces, 140. On the 

 transmission of sound, 145. On re- 

 sonance, 146. On the velocity of 

 the electric fluid, 284. On the 

 spectrum of theVoltaic spark, 295. 



Willis, Mr., his speaking-reed, 147. 



Wollaston, Dr., on the extent of 

 the atmosphere, 101. On the ex- 

 tent of hearing, 125. On refrac- 

 tion, 151. Discovers the chemical 

 rays and dark lines of the solar 

 spectrum, 157, 194. On rotatory 

 motion by the electro-magnetic 

 force, 315. On the light of the 

 celestial bodies, 362. 



Y. 



Year, civil or tropical, and sidereal 

 years, 77 et seq. 



Young, Dr. Thomas, on the compres- 

 sion of substances, 73. His hiero- 

 glyphic researches, 84. On capil- 

 lary attraction, 109. On the love 

 of harmony, 136. Establishes the 

 undulatory theory of light, 163. 

 On the interference of light, 169. 

 On radiant heat, 230. 



Z. 



Zodiacal light, supposed to be the 

 atmosphere of the sun, 379; or, 

 according to La Place and Profes- 

 sor Olmsted, a nebulous body re- 

 volving in the plane of the solar 

 equator, 385. 



THE END 



