INDEX. 



509 



PARATHERMIC. 



oxygen, 344 ; in antithesis to dia- 

 magnetism, 347 ; neutral substances 

 obtained by combinations of dia- 

 magnetism and, ib. ; Dr. Tyndall's 

 experiments on polarity of, 348 ; 

 dependent on arrangement of mole- 

 cules, 350, 351 ; affected by com- 

 pression, 351 ; truth establishing 

 its identity with diamagnetism, 356, 

 357. 



Parathermic rays, analyzed by Sir 

 John Herschel, 217-219. 



Paris, variation in length of the pen- 

 dulum at, 51 ; mean annual tem- 

 perature, 228 ; temperature of an 

 Artesian well in, 230. 



Paths of comets, 359, 360 ; secrets 

 disclosed by their excentricities, 365. 



Parry, Sir Edward, turned back by 

 the Polar current, 101 ; mean tem- 

 perature calculated from observa- 

 tions of, 245 ; thermometer at Mel- 

 ville Island marked by, 247. 



Pauxis, the Straits of, ebb and flow of 

 the sea in, 98. 



Peel, Sir William, thunderstorm ex- 

 perienced by, 293, 294. 



Pegasus, nebulous region of, 417. 



Pendulum, the, principle equalizing 

 its oscillations, 50 ; the earth's 

 figure calculated by, 50, 51 ; ex- 

 periments ascertaining the earth's 

 density, 57 ; isochronous, a measure 

 of time, 83 ; a standard of the mea- 

 sure of extension, 89 ; the, a con- 

 necting link between time and force, 

 94 ; inventions to neutralise the 

 effects of temperature, 272. 



Penumbra, in lunar eclipse, breadth 

 of space occupied by, 40. 



Perigee, of the lunar orbit, period of 

 its revolution, 37, 38 ; cause of its 

 rapid motion, 55. 



, solar, periods of its coincidence 



with the equinoxes, 86. 



Perihelion of a planet's path defined, 16. 



of the earth's orbit, its position 



regulating the length of seasons, 74. 



Periodic inequalities of planets, 13, 

 14; law from which they are de- 

 duced, 24, 25 ; of Jupiter's satel- 

 lites, 28, 29 ; lunar, 35. 



PHOSPHORESCENCE. 



Perkins, Mr., experiments of, testing 

 the laws of compression, 78. 



Peron, M., specific diversity of marine 

 animals asserted by, 254. 



Perpendicular force, the source of pe- 

 riodic inequalities, 15 ; effects pro- 

 duced by, 18. 



Perpetual motion, invariable propor- 

 tion between heat and force pre- 

 cluding, 279. 



Perseus, variable star in, 390, 391. 



Peters, Mr., comet discovered by, 370 ; 

 parallax of a. Lyrae, 388, 389 ; dis- 

 tances of fixed stars calculated, 389 ; 

 his theory of Sirius' irregular mo- 

 tions, 392 ; sun's motion proved 

 by, 405. 



Petit, M., observations of, on meteoric 

 satellites, 423. 



Peru, arcs of the meridian measured 

 in, 48. 



Phases of the moon, regulating returns 

 of eclipses, 39. 



Phenomena, of effects of light in 

 eclipses, 41, 42 ; applied to com- 

 puting longitudes, 43 ; caused by 

 tidal oscillation, 96 ; from force of 

 cohesion, 106, 107 ; of capillary 

 attraction, 115; produced by re- 

 fraction and reflection, 155-157 ; by 

 polarization of light, 186-190 ; ex- 

 hibited in fluorescence of light, 196, 

 197 ; resulting from interaction of 

 rays and molecules, analogous to 

 effects of photography, 219-222 ; 

 phosphorescent, 295, 296 ; of gal- 

 vanism, 310 ; of magnetism, 335, 

 345-348 ; magnecrystallic, 349, 

 350 ; exhibited by comets, 363, 

 364, 369, 370, 372-376 ; by the 

 Milky Way, 385-387 ; by variable 

 stars, 390-393 ; by double stars, 

 397-401; by nebula?, 409-415, 

 417-419; by meteoric showers, 

 421, 422. 



Phosphorescence, rays of the solar 

 spectrum exciting, 216; cause of, 

 in the solar spectrum, 217 ; excited 

 by electricity, 294 ; fish possessing 

 the property of, 295 ; the glow 

 discharge, 295, 296 ; experiments 

 investigating the nature of, 296. 

 z 3 



