[ 5 



November period, meteors of the, 



573, 581. 

 "Nubecula Major and Minor, 301, 



340. 

 Number and epoch of discovery of 



the principal planets, 403. 

 Nutation of the Earth's axis, 427, 



454. 



October, falling stars in, 580. 



Gibers' conjecture as to the aste- 

 roids being fragments of a single 

 destroyed planet, 509 ; on shoot- 

 ing stars, 583. 



Orbits, inclination of, planetary, 

 449; cometary, 557. 



Orion, nebula in the sword of, 298, 

 326 ; in the head of, 326 ; trape- 

 zium not surrounded by a nebula, 

 330 ; new stars discovered in the 

 trapezium, 330. 



Pallas, discovery of, 421; elements, 



506. 



Parthenope, discovery of, 421 ; ele- 

 ments, 508. 



Penumbrse of the solar body,317. 

 Periodic meteors, number of, ob- 

 served at different hours, and in 



different months, 577- 

 Perpetual spring, its undesirable 



nature, 451. 

 Perseus, falling stars issuing from, 



574. 

 Peruvian seven-day week, an error, 



418. 

 Poter Martyr, his description of 



the Magellanic Clouds, 340; on 



a fall of aerolites, 587. 

 Photosphere of the nebulous stars, 



322 ; of the Sun, 363. 

 Picard investigates the nebula in 



Orion, 299. 



Pisces, nebulous region of, 313. 

 Planetary discovery, epochs of, 



357. 

 Planetary motion, three great laws 



of, 599. 

 Plar.etary nebulae, 320; mainly found 



in the southern hemisphere. 320. 



Planetary system, stability of, how 

 demonstrated, 600. 



Planets and their satellites, general 

 considerations, 402 ; principal 

 planets, 403; discovery, 403; 

 names, 407 ; planetary signs, not 

 of ancient date, 411 ; days and 

 metals named from, 411; early 

 conjectures that other planets 

 remained to be discovered, 419 ; 

 periods of discovery since the 

 invention of the telescope, 420 ; 

 classification in two groups, 422 ; 

 exterior, generally larger than the 

 interior, 424; absolute and appa- 

 rent magnitudes, 426 ; arrange- 

 ment and distances, 429 ; as- 

 sumed laws, by Titius and Bode, 

 and Wurm, 442 ; masses, 445 ; 

 densities, 446; periods of revo- 

 lution, and axial rotation, 448 ; 

 inclination, 449 ; excentricity, 

 457; intensity of the Sun's light, 

 461. 



Planets, secondary, numerical data, 

 462. 



Planets, the small, numerical data, 

 504; table of elements, 508 j 

 Gibers' conjecture as to their 

 origin, 509. 



Plateau on irradiation, 487. 



Principal planets, 403. 



Proselenes, astronomical myth of 

 the, 439. 



Ptolemy mentions nebulous stars, 

 294. 



Regular nebulae, classification of, 

 315. 



Revolution, periods of, of the pla- 

 nets, 448 ; of comets, 553. 



Rhea, a satellite of Saturn, 523. 



Robinson, Dr., nebulae resolved by, 

 304. 



Rosse, Earl of, discoveries by means 

 of his powerful telescope, 304 ; 

 his caution, 306. 



Sabbath, used as a name for the 

 whole week. 413. 



