An introduction to astronomy: designed as a text-book for the use of students in college. By Denison Olmsted ...

X11 ANALYSIS.
Art. Art.
Direction in which the eclipse passes Establishment of a port............. 291
on the sun's disk................. 269 Tides on the coast of North America,
Greatest duration of total darkness.. 269 whence derived................... 292
Eclipses of the sun more frequent Why no tides in lakes and seas...... 293
than of the moon, why?.......... 269 Intricacy of the problem of the tides. 294
Lunar eclipses oftener visible, why?. 269 Atmospheric tide............. 295
Radiation of light in a total eclipse of Chapter IX.- THE PLANETS - INFERIOR
the sun.......................... 269D
the- su~.269~ 1l 1 PLANETS-MERCURY AND VENUS.
Interesting phenomena of a total
eclipse of the sun................ 271 Signification of the term planet...... 296
Baily's Beads................ 271 Planets known from antiquity....... 296
Flame-colored projections............ 271 Planets added in 1781 and 1846..... 296
Asteroids.......................... 296
Chapter VIII.-LONGITUDE-TIDES. Asteroids 296
Primary and Secondary Planets disObjects of the ancients in studying tinguished................... 296
astronomy...................... 272 Number of each.................... 296
Ditto of the moderns............... 272 Inclination of the planetary orbits to
LONGITUDE.-How to find the differ- the ecliptic...... 297
ence of longitude between two Inferior and Superior planets distinplaces................. 273 guished.......................... 298
Method bythe Chronometer explained 274 How the planets differ among themHow to set the chronometer to Green- selves............................ 298
wich time,................. 274 Distances from the sun in miles...... 299
Accuracy of some chronometers..... 274 Great dimensions of the planetary
Objections to them.................. 274 system............. 299
Longitude by eclipses explained..... 275 Illustrated by the motion of a railway
Lunar method of finding the longi- car.............................. 299
tude.............................2. 76 Order by which the distances of the
Circumstances which- render this planets increase................... 299
method somewhat difficult........ 277 Bode's law of distances............. 299
Difference of longitude accurately ob- Mean distances, how determined.... 299
tained by magnetic telegraph...... 278 Diameters in miles............... 300
TIDEs, —defined.................. 279 Great diversity in respect to magniHibh, Low, Spring; Neap, Flood, and tude............................. 300
Ebb Tide, severally defined...... 279 How the real diameters are found from
Similar tides on opposite sides of the the apparent. 300
earth................. 279 Periodic Times in months and years 301
Interval between two successive high Which of the planets move rapidly
tides........ 279 and which slowly................. 301
Average height for the whole globe.. 279 INFERIOR PLANETs.- -Proximity to the
Extreme height............ 279 sun.................... 302
Cause of the tides............. 280 Illustration by Fig. 60............... 302
Explain by figure 56............... 281 Conjunction deffned- inferior and
Tide-wave defined............... 281 superior....303................ 303
Comparative effects of the sun and Synodical revolution defined........ 304
moon in raising the tide........... 282 /low to find the synodical from the
Why the moon raises a higher tide sidereal.......................... 304
than the sun................... 282 Motion of an inferior planet, when
Spring tides accounted for.......... 283 direct and when retrograde........ 305
Neap tides, ditto........... 283 How these motions are affected by the
Power of the sun or moon to raise the earth's motions.............. 305
tide, in what ratio to its distance... 284 When the inferior planets are stationInfluence of the declinations of the ary.............................. 306
sun and moon on the tides........ 285 Elongation of the stationary points
Explain from figures 57 and 58....... 285 for Mercury and Venus........... 306
Motion of the tide-wave not progres- Phases of the inferior planets........ 307
sive............................ 286 Relative distances from the sun...... 308
Tides of rivers, narrow bays, how Eccentricity of their orbits.......... 309
produced........................ 287 Mode of finding the period in time.. 310
Cotidal Lines defined............... 287 Whlen is an inferior planet brightest? 311
Derivative and Primitive tides distin- Diurnal revolutions of Mercury and
guished...................... 287 Venus........................... 312
Velocity of the tide-wave, circum- Venus as the morning and evening star 313
stances which affect it............. 288 Phenomena every eight years....... 314
Explain by figure 59............... 289 TRANSITS OF THE INFERIOR PLANETS
Examples of very high tides........ 289 DEFINED.......... 315
Unit of altitude defined............. 290 When they occur-why not at every
Unit of altitude for different places.. 290 inferior conjunction............... 315