S 72 



236. Constitution of, com- 

 plicated, 237. Toughness 

 of, distinct from hardness ; 

 tenacity of, 238. Become 

 liquefied by the addition 

 of heat, 321. 



Sounds, musical, illustrative 

 of the analysis of pheno- 

 mena, 85. Means of having 

 a knowledge of, 89. Pro- 

 pagation of, through the air, 

 246. Newton's analysis of, 

 247. 



Standard measurement, neces- 

 sity of, 125. Laws of na- 

 ture used as such, illus- 

 trated by the rotation of the 

 earth, 126. 



Substances all subject to dila- 

 tation by the addition of 

 heat, 243. 



Sun, the character of the heat 

 of, 315. 



Thales, philosophy of, 107. 



Theories, how to estimate the 

 value of, 204. Best ar- 

 rived at by the consideration 

 of general laws, 208. Ex- 

 planatory of the phenomena 

 of nature ; on what their 

 application ought to be 

 grounded, 209. 



Thomson, Dr., his opinion of 

 the atomic weights, 307. 



Thermometer, air, 319. 



Thermo-electricity, 341. 



Time, division of, 126, 127. 



Torricelli, pupil of Galileo, 



his experiments proving the 



weight of atmosphere, 229 



Torpedo, shock of, 341, 342. 



Ulugh Begh, his catalogue 

 of stars, 277. 



Vaccination, success of, as a 

 preventive to small-pox, 

 52. 



Vision and light, ignorance of 

 the ancients respecting, 249. 



Volta, his discoveries in elec- 

 tricity, 335. Electric pile 

 of, 337. 



Voltaic circuit, 338. 



Water, effects of the power of, 

 61. 



Whewell, his experiments, 

 187. 



Wells, Dr., his theory of dew 

 163. 



Wind, effects of the power of, 

 6'. 



Wire steel, magnetized masks 

 of, used by needle-makers, 

 57. 



Wollaston, Dr., his verification 

 of the laws of double re- 

 fraction in Iceland spar, 

 258. His invention of the 

 goniometer, 292. 



World, the materials of the, 

 290. 



Young, Dr., his experiments 

 on the interference of the 

 rays of light, 260. 



Zoology, fossil, 344, 



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