518 



PHYSICAL SCIENCES. 



SUNBEAMS. 



atmospheres, ib. ; variations in heat 

 and light emitted from, 225, 226 ; 

 amount of heat annually received by 

 the earth from, 238 ; effect of his 

 brilliancy on the heat emitted by, 

 259 ; his position affecting varia- 

 tions in the magnetic elements, 343, 

 34-4; connexion between periodic 

 variation in his spots and in the 

 magnetic elements, 344 ; vast sweep 

 of his gravitating force, 365 ; in- 

 creased attraction of, for comets, 

 372 ; gulfs separating stars from, 

 390 ; possibility of change in his 

 lustre, 394 ; spot on, measured by 

 Sir John Herschel, 394, 39o ; pro- 

 portion of his light to the moon's, 

 404 ; rate and orbit of motion with 

 his system, 405, 406 ; a nebulous 

 star, 412 ; meteoric nebula revolv- 

 ing round, 422 ; gravitating force 

 of, 4*24, 425. 



Sunbeams, resolved into their com- 

 ponent colours, 159-162 ; law pre- 

 vailing in the phenomena of, 198; 

 light a distinct property of, 214; 

 resolved into three spectra, 222 ; 

 undulations constituting, 223 ; their 

 influence on vegetation, 249. 



Swan, the, vanishing star in, 393. 



Switzerland, meteors falling in, 421. 



Syene, arc of the meridian measured 

 between Alexandria and, 49. 



Sykes, Colonel, extensive range of cul- 

 tivation of wheat observed by, 250. 



Sympathetic vibrations in musical in- 

 struments, 147-149. 



Syren, the, an instrument ascertaining 

 the number of musical pulsations in 

 a secontj, 143. 



Syzigies, tides increased in the, 96. 



TABLE-LANDS, high, influence of, on 

 the atmosphere, 241. 



Tail of comets, sudden development 

 of, 372 ; forces producing, 375 ; 

 unequal illumination of, 375, 376 ; 

 change in position of, 376 ; divided, 

 ib. ; constitution of, 377. 



Talbot, Fox, his inventions in photo- 

 graphy, 204. 



Tangent, a, to planetary orbits, planets 



TEMPERATURE. 



impelled in the direction of, 8 ; 

 force, disturbing, in the direction of, 

 14, 15 ; deflection from, a mea- 

 surement of centrifugal force, 49. 



Tangential force, occasioning secular 

 inequalities, 14 ; effects produced 

 by, 15; producing the variation 

 of the moon, 35 ; force acting on 

 the sea, 100. 



velocity, effects produced by 



modifications of, 16 ; undiminished 

 by the ethereal medium, 22. 



Telegraph, the electric, discovery 

 leading to the invention of, 323, 

 324 ; the Atlantic, 325 ; principles 

 of its construction, 326, 327 ; date 

 of its completion, 327. 



Telegraphs, land, principle of their 

 construction, 328. 



Telescope, the achromatic, principle 

 of its construction, 164. 



, the differential, differences in 



illumination determined by, 227. 



, Lord Rosse's, nebulae resolved 



by, 407, 415. 



Telescopium, comet traversing the con- 

 stellation of, 379 ; nebula in, 414. 



Temperature, a decrease in, affecting 

 the earth's rotation, 72 ; excen- 

 tricity of the terrestrial orbit, a 

 cause of decreasing, 73 ; law equal- 

 ising, 74; geological changes af- 

 fecting, 75. 



, varying in the terrestrial at- 

 mosphere, zone of constant, 119 ; 

 affecting atmospheric: undulations, 

 121 ; modifying the velocity of 

 sound, 134; chemical action of 

 light affected by, 218-222 ; of the 

 ethereal medium, 227, 228 ; under- 

 ground stratum of constant, 228 ; 

 rate of increase in, below the earth's 

 crust, 228, 231 ; of the ocean, 

 231 ; mode of finding annual aver- 

 age, 239 ; causes of disturbance 

 in regular variation of, 240-245 ; 

 variations in the same latitude, 

 246, 247 ; influence of, on vegeta- 

 tion, 248 ; affecting transmission 

 of heat, 259, 260 ; of solid bodies, 

 caused by absorption of rays, 268 ; 

 affecting the length of the pendu- 



