INDEX. 



519 



TENEUIFFE. 



him, 272 ; causes of perpetual 

 variations in, 274 ; transmission of 

 electricity affected by, 284 ; affect- 

 ing magnetism, 352. 



Teneriffe, the Peak of, prevailing 

 winds on, 1 24 ; lunar heat on, 227 ; 

 zones of vegetation, 250 ; character 

 of itsfloia, 252. 



Terrestrial globe, the, a magnet, 336. 



magnetism, 341-343 ; the three 



elements and their variations, 343, 

 344 ; storms, period of their varia- 

 tion, 344 ; its connexion with solar 

 magnetism, ib. ; effect of atmo- 

 spheric magnetism on, 345 ; pro- 

 bable cause of, 346; effect of 

 planetary magnetism on, 346, 347. 



meridian, a, defined, 46. 



Tessular system of crystallization, 108. 



Texas, monsoons occasioned by its 

 deserts, 124. 



Thames, the, period occupied by the 

 tidal wave in reaching, 94. 



Thaw, cause of the sensible chilliness 

 of, 276. 



Theory of probabilities, use of, in 

 determining astronomical data, 60. 



Thermo-electric currents, discovery 

 of, 332 ; phenomena exhibited by, 

 333 ; principle of, applied to mea- 

 suring heat, 333, 334. 



Thcrmography, examples of, 219- 

 221. 



Thermometer, the, principles applied 

 to the construction of, 113; con- 

 sulted in determining mountain 

 heights, 1 19, 1 20 ; refraction vary- 

 ing with, 154 ; heat measured by 

 motion in, 274. 



Thermomultiplier, use of, in experi- 

 ments, 264 ; principle of its con- 

 struction, 333, 334. 



Theta Orionis, the multiple system 

 of, 395. 



Thibet, wheat ripening in, 250. 



Thomas, St., the island of, hurricane 

 with pauses at, 127. 



Thomson, W., Professor, experiments 

 of, in freezing water, 271 ; dyna- 

 mical theory of heat maintained 

 by, 275 note; his calculation of 

 the force exerted in vibrations of 



TOURMALINE. 



light, 279 ; investigation into the 

 relations of light and magnetism, 

 320 ; density of the ethereal me- 

 dium computed by, 356; magnetic 

 property of the ethereal medium 

 pleaded for, 357. 



Thunder, theory of prolonged peals of, 

 138. 



Tidal wave, theory of, 92 ; its birth- 

 place, 93 ; course of, 93, 94 ; 

 velocity, 94 ; effect of depth on its 

 motion, 95. 



Tides, calculation from the moon's 

 action on, 55 ; theory of forces 

 producing, 91, 92 ; circumstances 

 occasioning irregularities, 93 ; ris- 

 ing, progress of, 93, 94 ; three 

 kinds of oscillations in, 95, 96 ; 

 variations in, from lunar and solar 

 influence, 96-98 ; effect of inter- 

 ference of waves on, 99 ; the sea's 

 equilibrium undeianged by, 100. 



, lunar and diurnal, of the ter- 

 restrial atmosphere, 121 ; examples 

 of sympathetic undulation, 148. 



Time, a measure of motion, 58 ; a 

 measure of angular motion, 83 ; 

 difference between mean and ap- 

 parent solar, 84 ; mean equinoctial, 

 mode of computing its object, 86 ; 

 estimation of, corrected by means 

 of laws of unequal expansion, 272. 



Timocharis, comp;msou of his obser- 

 vations with Hipparchus, 80. 



Tomboro, submerged in a volcanic 

 eruption, 233. 



Torpedo, the, electrical action of, 310, 

 311. 



Torrecelian vacuum, experiment on 

 the electric discharge in the, 306 ; 

 lines of magnetic force passing 

 through, 344. 



Torronto, observations on magnetic 

 storms at, 346. 



Toucan, comet approaching the con- 

 stellation of, 379 ; a nebula in, 414. 



Toucani, 47 ; globular nebulous clus- 

 ter, 414. 



Tourmaline, brown, light polarized 

 by prisms of, 180 ; property quali- 

 fying it to analyze polarized light, 

 182 ; coloured images produced by, 

 2 A 2 



