INDEX. 



493 



FLUOR-SPAR. 



Fluor-spar, its property of diminish- 

 ing refrangibility of light, 196. 



Fluorescence of light, definition of, 

 195 ; vibrations of the substance 

 producing, 196; experiments, 197, 

 198. 



Focus of a meteoric shower, 422. 



Fog, yellow, excluding the chemical 

 action of rays, 214. 



Forbes, Professor, temperature of the 

 boiling point ascertained by, 120 ; 

 observations of, on rayless lines, 

 163; lunar heat tested by, 227; 

 experiments of, in polarization of 

 heat, 264, 267. 



Force, relation of, to heat, 275 ; 

 transforming solids to liquids and 

 to vapour, 275, 277 ; a power of 

 nature, 279 ; light and heat modes 

 of, 219, 220; heat a living, 329; 

 lines of magnetic, 338, 340 ; con- 

 servation of, maintained in periodic 

 variation of atmospheric magnetism, 

 345 ; increatable, indestructible, 



353 ; examples of conservation of, 



354 ; fundamental principle of con- 

 servation, 357 ; influence and ac- 

 tion of the gravitating, 424, 426. 



Forces, the unknown cause of motion, 

 5 et passim ; counteraction of solar 

 and tangential, in planetary motion, 

 8 ; adjustment of, ensuring the 

 permanence of the solar system, 11 

 12 ; three partial, causing perturb- 

 ation in planetary motion, 14, 15; 

 excess of equatorial diameter the 

 origin of, 27, 28 ; three, disturbing 

 lunar motions, 34, 35 ; determin- 

 ing planet Jorins, 44, 45 ; produc- 

 ing tides, 91, 92 ; combining to 

 form the centrifugal, 100 ; acting 

 on molecules of matter, 102, 105 

 producing capillary phenomena 

 1 14 ; latent, in nature, 279, 280 ; 

 one universal power, the root o: 

 all, 321 ; exact balance of, in elec- 

 tricity, 334 ; kindred and con- 

 vertible, 353 ; developing comets 

 tails, 375 ; determining the forms o: 

 orbits, 382, 383 ; maintaining the 

 stability of the solar system, 426 

 mutual relations of, 427. 



FRICTION. 

 "orests, change produced in the at- 

 mosphere by, 241, 243 ; number 

 of species of trees found in American 

 and European, 252. 

 Formentera, quadrant of the meridian 

 passing through, furnishing a unit 

 of linear measure, 89. 

 Fornax, nebulous patches crossing, 



417. 



Forster, Lieutenant, conversation car- 

 ried on by, across Port Bowen Har- 

 bour, 136. 

 Fossil plants, an evidence of change 



in temperature, 74. 

 Fourrier, mean temperature of space 

 according to, 119 ; rate of decrease 

 in the earth's central heat com- 

 puted by, 232. 



Fox, Mr., temperatures in mines 

 tested by, 228, 229 ; law of pa- 

 ramagnetic force ascertained by, 

 338 ; observations in mines, prov- 

 ing agency of electro-magnetism, 

 346. 



France, arcs of the meridian mea- 

 sured in, 48 ; unit of linear mea- 

 sure in, 89 ; mode of arithmetical 

 computation, 90 ; atmospheric 

 pressure in, 120 ; cliffs of, seen 

 from Hastings, 157. 

 Fraanhofer, M., discovery of rayless 

 lines in the solar spectrum, 1 62 ; 

 comparative refrangibility of rays 

 ascertained by, 163 ; data furnished 

 by, to determine the dispersive 

 power of rays, 165 ; his discovery 

 determining the length of waves 

 independently of refraction, 201 ; 

 spectrum of an electric spark ob- 

 served by, 289. 



Freezing, temperature required for, 

 under pressure, 271 ; theory of, 

 276. 



Fresnel, M., his testimony in favour 

 of the undulatory theory of light, 

 171 ; theory of refraction, 183 ; 

 discoveries in polarization of light, 

 191, 193. 

 Freyberg, green plants found in mines 



at, 253. 



Friction evolving heat, 274, 275; 

 electricity, 282, 283. 



