52-2 



INDEX. 



Secular variations of inclination, 24. 



Notes 72, 75. 

 in the obliquity of the ecliptic, 26. 



Notes 79, 143, 148. 



of Jupiter, 22. 



of Jupiter's satellites, 32. 



of the moon, 41. 



Seebeck, Professor, on the maximum 



point of heat in the solar spectrum, 



248. 



Shell-fish, the weight they sustain, 131. 

 Shooting stars, 447. 

 Sidereal day, 93. 



revolution, 93. 



astronomy, 445. 



Sine of an arc or angle, 23. Note 76. 

 Sirius, distance and light of, 427. 

 Smyth, Capt., measures the height of 



Etna, 133. His observations of 7 



Virginis, 418. 



Snow, line of perpetual, 291. 

 Solar system, its motion in space, 7, 27, 



414. 



, perpetual stability of, 24. 

 , spectrum, 1?8, 180, 223, 247. 



, heat, quantity of, 288. 



, distribution of, 289. 



Solstices, 97. Note 148. 

 Sothaic period, 96. 

 Sound, theory of, 143. 

 , undulations producing, 144. Note 



156. 



, intensity of, 146, 152. 



, velocity of, 150. 



, transmission of, 143 et seq. 



, reflection of, 153. 



-, refraction and interference of, 154. 



Sounds, musical, 156. 



, harmonic, 157. 



Space, 6. Note 21. 



, temperature of, 276. 



Speaking-machine, 169. 

 Sphere, attraction of, 5. 

 Spheroid, 5. Note 9. 



, attraction of a, 6. Note 12. 



Spring, 26. 



tides, 106. 



Square of distance, 6. Note 23. 



of moon's distance, 6. 



of sine and cosine of latitude, 52. 



Note 123. 

 number and its rout. Note 132. 



Stability of solar system, 24. 



Stars, fixed, 413. 



, parallax of, 61,427. 



, distance of, 61, 426. 



, distances of, known from the 



binary systems, 416, 428. 



, number of, 413. 



, magnitude of, 428. 



that have vanished, and new stars, 



422. 



, variable, 423, 424. 



, their motions, 419, 420, 428, et seq. 



, double, 416 et seq. 



, parallactic motions of, 426. 



, binary systems of, and their orbits, 



416 et seq. 



, their angular velocities, how ob- 

 tained, 418. 



, triple and quadruple, 420. 



, clusters of, 433, 438. 



, co lours of, 421. 



, periodical, 423, 424, 425, 



Steam, 261 et seq. 



Struve, Professor, on the rings of Sa- 

 turn, 77- On Halley's comet, 391- 

 On the double stars, 422. 



Sun, the centre of gravitation, 7- 



, motion of, 9, 432. 



, magnitude of, 63, 64. 



, eclipses of, 46. 



, parallax and distance of, 60. 



, mass of, 63. 



, rotation of, 74. 



, constitution of, 274. 



, light and atmosphere of, 274. 



, spots on, 274. 



, heat of, 287, 288. 



Surfaces vibrating, 161. 



Svanberg, M., on the temperature of 

 space, 276. 



Sykes, Col., on the height at which 

 wheat grows , 302. 



Synodic revolution, 46. Note 112. 



Syren, 160. 



Syrup, physical properties of, 213. 



System, solar, its stability, 24. 



, its motion, 7, 414. 



of Jupiter and his satellites, 32. 



of binary stars, 416. 



Syzygies, 105. Note 153. 



