Part 41

_Astronomy_, the great advantages arising from it both in our religious and civil concerns, 1 Discovers the laws by which the Planets move, and are retained in their Orbits, 2 _Atmosphere_, the higher the thinner, 174. It’s prodigious expansion, _ib._ It’s whole weight on the Earth, 175. Generally thought to be heaviest when it is lightest, 176. Without it the Heavens would appear dark in the day-time, 177. Is the cause of twilight, _ib._ It’s height, _ib._ Refracts the Sun’s rays, 178. Causeth the Sun and Moon to appear above the Horizon when they are really below it, _ib._ Foggy, deceives us in the bulk and distance of objects, 185.

_Attraction_, 101-105. Decreases as the square of the distance increases, 106. Greater in the larger than in the smaller Planets, 158. Greater in the Sun than in all the Planets if put together, _ib._

_Axes of the Planets_, what, 19. Their different positions with respect to one another, 120.

_Axis of the Earth_, it’s parallelism, 302. It’s position variable as seen from the Sun or Moon, 338. the Phenomena thence arising, 340.

B.

_Bodies_, on the Earth, lose of their weight the nearer they are to the Equator, 117. How they might lose all their weight, 118, How they become visible, 167.

C.

_Calculator_, (an Instrument) described, 436.

_Calendar_, how to inscribe the Golden Numbers rightly in it for shewing the days of New Moons, 423.

_Cannon-Ball_, it’s swiftness, 89. In what times it would fly from the Sun to the different Planets and fixed Stars, _ib._

CASSINI, his account of a double Star eclipsed by the Moon, 58. His Diagrams of the Paths of the Planets, 138.

_Catalogue_ of the Eclipses, 327. Of the Constellations and Stars, 367. Of remarkable _Æras_ and events, 433.

_Celestial Globe_ improved, 438.

_Centripetal and centrifugal forces_, how they alternately overcome each other in the motions of the Planets, 152-154.

_Changes in the Heavens_, 403.

_Chords_, line of, how to make, 369.

_Circles_, of perpetual Apparition and Occultation, 128. Of the Sphere, 198. Contain 360 Degrees whether they be great or small, 207.

_Civil Year_, what, 411.

COLUMBUS (CHRISTOPHER) his story concerning an Eclipse, 330.

_Clocks_ and _Watches_, an easy method of knowing whether they go true or false, 223. Why they seldom agree with the Sun if they go true, 228-245. How to regulate them by Equation Tables and a Meridian line, 225, 226.

_Cloudy Stars_, 402.

_Cometarium_ (an Instrument) described, 437.

_Constellations_, antient, their number, 396. The number of Stars in each, according to different Astronomers, 399.

_Cycle_, Solar, Lunar, and _Romish_, 420. Of _Easter_, 425.

D.

_Darkness_ at our SAVIOUR’s crucifixion supernatural, 352, 432.

_Day_, natural and artificial, what, 417. And _Night_, always equally long at the Equator, 126. Natural, not compleated in an absolute turn of the Earth on it’s Axis, 222.

_Degree_, what, 207.

_Digit_, what, 321, _n._

_Direction_, (Number of) 426.

_Distances of the Planets from the Sun_, an idea thereof, 89. A Table thereof, 98. How found, 190.

_Diurnal_ and _annual Motions_ of the Earth illustrated, 200, 202.

_Dominical Letter_, 427.

_Double_ projectile force, a balance to a _Quadruple_ Power of Gravity, 153. Star covered by the Moon, 58.

E.

_Earth_, it’s bulk but a point as seen from the Sun, 3 It’s Diameter, annual Period, and Distance from the Sun, 47. Turns round it’s Axis, _ib._ Velocity of it’s equatoreal Parts, _ib._ Velocity in it’s annual Orbit, _ib._ Inclination of it’s Axis, 48. Proof of it’s being globular, or nearly so, 49, 314. Measurement of it’s surface, 50, 51. Difference between it’s Equatoreal and Polar Diameters, 76. It’s motion round the Sun demonstrated by gravity, 108, 111. by Dr. BRADLEY’s observations, 113. by the Eclipses of Jupiter’s Satellites, 219. It’s diurnal motion highly probable from the absurdity that must follow upon supposing it not to move, 111. 120. and demonstrable from it’s figure, 116. this motion cannot be felt, 119. Objections against it’s motion answered, 112, 121. It has no such thing as an upper or under side, 122. in what case it might, 123. The swiftness of it’s motion in it’s Orbit compared with the velocity of light, 197. It’s diurnal and annual motions illustrated by an easy experiment, 200. Proved to be less than the Sun and bigger than the Moon, 315.

_Easter Cycle_, 425.

_Eclipsareon_ (an Instrument) described, 442.

_Eclipses_, of Jupiter’s Satellites, how the Longitude is found by them, 207-218. they demonstrate the velocity of light, 216. Of the Sun and Moon, 312-327. Why they happen not in every month, 316. When they must be, 317. Their limits, _ib._ Their Period, 320, 326. A dissertation on their progress, 321-324. A large catalogue of them, 327. Historical ones, 328. More of the Sun than of the Moon, and why, 331. The proper Elements for their calculation and projection, 353-390.

_Ecliptic_, it’s Signs, their names and characters, 91. Makes different Angles with the Horizon every hour and minute, 275. how these Angles may be estimated by the position of the Moon’s horns, 260. It’s obliquity to the Equator less now than it was formerly, 405. How it’s Signs are numbered, 354.

_Elongations_, of the Planets, as seen by an observer at rest on the outside of all their Orbits, 133. Of Mercury and Venus as seen from the Earth, illustrated, 142. it’s quantity, 143. Of Mercury, Venus, the Earth, Mars, and Jupiter; it’s quantity as seen from Saturn, 147.

_Epochas_ or _Æras_, 433.

_Equation_ of time, 224-245. Of the Moon’s Place, 355. Of the Sun’s Place, _ib._ Of the Nodes, 363.

_Equator_, day and night always equal there, 126. Makes always the same Angle with the Horizon of the same place; the Ecliptic not, 274, 275.

_Equinoctial Points_ in the Heavens, their precession, 246, a very different thing from the recession or anticipation of the Equinoxes on Earth, the one no ways occasioned by the other, 249.

_Excentricities_ of the Planets Orbits, 155.

F.

_Fallacies_ in judging of the bulk of objects by their apparent distance, 185; applied to the solution of the horizontal Moon, 187.

_First Meridian_, what, 207.

_Fixed Stars_, why they appear of less magnitude when viewed through a telescope than by the bare eye, 391. Their number, 392. Their division into different Classes and Constellations, 395-399.

G.

_General Phenomena_ of a superior Planet as seen from an inferior, 149.

_Gravity_, demonstrable, 101-104. Keeps all bodies on the Earth to it’s surface, or brings them back when thrown upward; and constitutes their weight, 101, 122. Retains all the Planets in their Orbits, 103. Decreases as the square of the distance increases, 106. Proves the Earth’s annual motion, 108. Demonstrated to be greater in the larger Planets than in the smaller; and stronger in the Sun than in all the Planets together, 158. Hard to understand what it is, 160. Acts every moment, 162.

_Globe_, improved celestial, 438.

_Great Year_, 251.

H.

_Harmony_ of the celestial motions, 111.

_Harvest-Moon_, 273-293. None at the Equator, 273. Remarkable at the Polar Circles, 285. In what years most and least advantageous, 292.

_Heat_, decreases as the square of the distance from the Sun increases, 169. Why not greatest when the Earth is nearest the Sun, 205. Why greater about three o’Clock in the afternoon than when the Sun is on the Meridian, 300.

_Heavens_, seem to turn round with different velocities as seen from the different Planets; and on different Axes as seen from most of them, 120. Only one Hemisphere of them seen at once from any one Planet’s surface, 125. The Sun’s Center the only point from which their true Motions could be seen, 135. Changes in them, 403.

_Horizon_, what, 125, _n._

_Horizontal-Moon_ explained, 187.

_Horizontal Parallax_, of the Moon, 190; of the Sun, 191; best observed at the Equator, 193.

_Hour-Circles_, what, 208.

_Hour_ of time equal to 15 degrees of motion, _ib._ How divided by the _Jews_, _Chaldeans_, and _Arabians_, 419.

HUYGENIUS, his thoughts concerning the distance of some Stars, 5

I. J.

_Inclination_ of Venus’s Axis, 29. Of the Earth’s, 48. Of the Axis or Orbit of a Planet only relative, 201.

_Inhabitants_ of the Earth (or any other Planet) stand on opposite sides with their feet toward one another, yet each thinks himself on the upper side, 122.

_Julian Period_, 430.

_Jupiter_, it’s distance, diameter, diurnal and annual revolutions, 67-69. The Phenomena of it’s Belts, 70. Has no difference of seasons, 71. Has four Moons, 72, their grand Period, 73, the Angles which their Orbits subtend as seen from the Earth, 74, most of them are eclipsed in every revolution, 75. The great difference between it’s equatoreal and polar Diameters, 76. The inclination of it’s Orbit, and place of it’s Ascending Node, 77. The Sun’s light 3000 times as strong on it as Full Moon-light is on the Earth, 85. Is probably inhabited, 86. The amazing strength required to put it in motion, 158. The figures of the Paths described by it’s Satellites, 269.

L.

_Light_, the inconceivable smallness of it’s particles, 165, and the dreadful mischief they would do if they were larger, 166. It’s surprising velocity, 166, compared with the swiftness of the Earth’s annual motion, 197. Decreases as the square of the distance from the luminous body increases, 169. Is refracted in passing through different Mediums, 171-173. Affords a proof of the Earth’s annual motion, 197, 219. In what time it comes from the Sun to the Earth, 216, this explained by a figure, 217.

_Limits_ of Eclipses, 317.

_Line_, of the Nodes, what, 317; has a retrograde motion, 319. Of Sines and Chords, how to make, 369.

LONG (Rev. Dr.) his method of comparing the quantity of the surface of dry land with that of the Sea, 51. His glass sphere, 126.

_Longitude_, how found, 207-213.

_Lucid Spots_ in the Heavens, 401.

_Lunar Cycle_ deficient, 422.

M.

_Magellanic Clouds_, 402.

_Man_, of a middle size, how much pressed by the weight of the Atmosphere, 175; why this pressure is not felt, _ib._

_Mars_, it’s Diameter, Period, Distance, and other Phenomena, 64-67.

_Matter_, it’s properties, 99.

_Mean Anomaly_, what, 239.

_Mercury_, it’s Diameter, Period, Distance, &c. 22. Appears in all the shapes of the Moon, 23. When it will be seen on the Sun, 24. The inclination of it’s Orbit and Place of it’s Ascending Node, _ib._ It’s Path delineated, 138. Experiment to shew it’s Phases and apparent Motion, 142.

_Mercury_ (Quicksilver) in the Barometer, why not affected by the Moon’s raising Tides in the Air, 311.

_Meridian_, first, 207. Line, how to draw one, 226.

_Milky Way_, what, 400.

_Months_, _Jewish_, _Arabian_, _Egyptian_, and _Grecian_, 415.

_Moon_, her Diameter and Period, 52. Her phases, 53, 255. Shines not by her own light, 54. Has no difference of seasons, 55. The Earth is a Moon to her, 56. Has no Atmosphere of any visible Density, 58; nor Seas, 59. How her inhabitants may be supposed to measure their year, 62. Her light compared with day-light, 85. The excentricity of her Orbit, 98. Is nearer the Earth now than she was formerly, 163. Appears bigger in the Horizon than at any considerable height above it, and why, 187; yet is seen much under the same Angle in both cases, 188. Her surface mountainous, 252: if smooth she could give us no light, _ib._ Why no hills appear round her edge, 253. Has no Twilight, 254. Appears not always quite round when full, 256. Her phases agreeably represented by a globular Stone viewed in Sun-shine when she is above the Horizon, and the observer placed as if he saw her on the top of the Stone, 258. Turns round her Axis, 262. The length of her Solar and Sidereal Day, _ib._ Her periodical and synodical revolution represented by the motions of the hour and minute hands of a Watch, 264. Her Path delineated, and shewn to be always concave to the Sun, 265-268. Her motion alternately retarded and accelerated, 267. Her gravity toward the Sun greater than toward the Earth at her Conjunction, and why she does not then abandon the Earth on that account, 268. Rises nearer the time of Sun-set when about the full in harvest for a whole week than when she is about the full at any other time of the year, and why, 273-284: this rising goes through a course of increasing and decreasing benefit to the farmers every 19 years, 292. Continues above the Horizon of the Poles for fourteen of our natural Days together, 293. Proved to be globular, 314. and to be less than the Earth, 315. Her Nodes, 317. ascending and descending, 318. their retrograde motion, 319. Her acceleration proved from antient Eclipses, 322, _n._ Her Apogee and Perigee, 336. Not invisible when she is totally eclipsed, and why, 346. How to calculate her Conjunctions, Oppositions, and Eclipses, 355-390. How to find her age in any Lunation by the Golden Number, 423.

_Morning_ and _Evening Star_, what, 145.

_Motion_, naturally rectilineal, 100. Apparent, of the Planets as seen by a spectator at rest on the outside of all their Orbits, 133; and of the Heavens as seen from any Planet, 154.

N.

_Natural Day_, not compleated in the time that the Earth turns round it’s Axis, 222.

_New_ and _Full Moon_, to calculate the times of 355.

_New Stars_, 403, cannot be Comets, 404.

_New Style_, it’s original, 414.

NICIAS’s Eclipse, 328.

_Nodes_, of the Planet’s Orbits, their places in the Ecliptic, 20. Of the Moon’s Orbit, 317. their retrograde motion, 319.

_Nonagesimal Degree_, what, 259.

_Number of Direction_, 426.

O.

_Objects_, we often mistake their bulk by mistaking their distance, 185. Appear bigger when seen through a fog than through clear Air, and why, _ib._ this applied to the solution of the Horizontal Moon, 187.

_Oblique Sphere_, what, 131.

_Olympiads_, what, 323. _n._

_Orbits_ of the Planets not solid, 21.

_Orrery_ described, 434, 435, 436.

P.

_Parallax_, Horizontal, what, 190.

_Parallel Sphere_, what, 131.

_Path_ of the Moon, 265, 266, 267. Of Jupiter’s Moons, 269.

_Pendulums_, their vibrating slower at the Equator than near the Poles proves that the Earth turns on it’s Axis, 117.

_Penumbra_, what, 336. It’s velocity on the Earth in Solar Eclipses, 337.

_Period of Eclipses_, 320, 326.

_Phases of the Moon_, 252-268.

_Planets_, much of the same nature with the Earth, 11. Some have Moons belonging to them, 12. Move all the same way as seen from the Sun, but not as seen from one another, 18. Their Moons denote them to be inhabited, 86. The proportional breadth of the Sun’s Disc as seen from each of them, 87. Their proportional bulks as seen from the Sun, 88. An idea of their distances from the Sun, 89. Appear bigger and less by turns, and why, 90. Are kept in their Orbits by the power of gravity, 101, 150-158. Their motions very irregular as seen from the Earth, 137. The apparent motions of Mercury and Venus delineated by Pencils in an Orrery, 138. Elongations of all the rest as seen from Saturn, 147. Describe equal areas in equal times, 153. The excentricities of their Orbits, 155. In what times they would fall to the Sun by the power of gravity, 157. Disturb one another’s motions, the consequence thereof, 163. Appear dimmer when seen through telescopes than by the bare eye, the reason of this, 170.

_Planetary Globe_ described, 439.

_Polar Circles_, 198.

_Poles_, of the Planets, what, 19. Of the world, what, 122. Celestial, seem to keep on the same points of the Heavens all the year, and why, 196.

_Projectile Force_, 150; if doubled would require a quadruple power of gravity to retain the Planets in their Orbits, 153. Is evidently an impulse from the hand of the ALMIGHTY, 161.

_Precession of the Equinoxes_, 246-251.

_Ptolemean_ System absurd, 96, 140.

R.

_Rays of Light_, if not disturbed, move in straight lines, and hinder not one another’s motions, 168. Are refracted in passing through different mediums, 171.

_Reflection of the Atmosphere_ causes the Twilight, 177.

_Refraction of the Atmosphere_ bends the rays of light from straight lines, and keeps the Sun and Moon longer in sight than they would otherwise be, 178. A surprising instance of this, 183. Must be allowed for in taking the Altitudes of the celestial bodies, _ib._

_Right Sphere_, 131.

S.

_Satellites_; the times of their revolutions round their primary Planets, 52, 73, 80. Their Orbits compared with each other, with the Orbits of the primary Planets, and with the Sun’s circumference, 271. What sort of Curves they describe, 272.

_Saturn_, with his Ring and Moon’s, their Phenomena, 78, 79, 82. The Sun’s light 1000 times as strong to him as the light of the Full Moon is to us, 85. The Phenomena of his Ring farther explained, 204.

_Our blessed_ SAVIOUR, the darkness at his crucifixion supernatural, 352. The prophetic year of his crucifixion found to agree with an astronomical calculation, 432.

_Seasons_, different, illustrated by an easy experiment, 200; by a figure, 202.

_Shadow_, what, 312.

_Sidereal Time_, what, 221; the number of Sidereal Days in a year exceeds the number of Solar Days by one, and why, 222. An easy method for regulating Clocks and Watches by it, 223.

_Signs of the Zodiac_, their names and characters, 91, 365. How they are numbered by Astronomers, 354.

_Sines_, line of, how to make, 369.

SMITH, (Rev. Dr.) his companion between Moon-light and Day-light, 85. His demonstration that light decreases as the square of the distance from the luminous body increases, 169. (_Mr._ GEORGE) his Dissertation on the Progress of a Solar Eclipse, 321-324.

_Solar Astronomer_, the judgment he might be supposed to make concerning the Planets and Stars, 135, 136.

_Sphere_, parallel, oblique, and right, 131. It’s Circles, 198.

_Spring and Neap Tides_, 302.

_Stars_, their vast distance from the Earth, 3, 196. Probably not all at the same distance, 4 Shine by their own light, and are therefore Suns 7, probably to other worlds, 8 A demonstration that they do not move round the Earth, 111. Have an apparent slow motion round the Poles of the Ecliptic, and why, 251. A catalogue of them, 399. _Cloudy_, 402. New, 403. Some of them change their places, 404.

_Starry Heavens_ have the same appearance from any part of the Solar System, 132.

SUN appears bigger than the Stars, and why, 4 Turns round his Axis, 18. His proportional breadth as seen from the different Planets, 87. Describes unequal arcs above and below the Horizon at different times, and why, 130. His Center the only place from which the true motions of the Planets could be seen, 135. Is for half a year together visible at each Pole in it’s turn, and as long in visible, 200, 294. Is nearer the Earth in Winter than in Summer, 205. Why his motion agrees so seldom with the motion of a well regulated Clock, 224-245. Would more than fill the Moon’s Orbit, 271. Proved to be much bigger than the Earth, and the Earth to be bigger than the Moon, 315. To calculate his true place, 360.

_Systems_, the Solar, 17-95; the Ptolemean, 96; the Tychonic, 97.

T.

_Table_, of the Periods, Revolutions, Magnitudes, Distances, _&c._ of the Planets, facing § 99. Of the Air’s rarity, compression, and expansion at different heights, 174. Of refractions, 182. For converting time into motion, and the reverse, 220. For shewing how much of the celestial Equator passes over the Meridian in any part of a mean Solar Day; and how much the Stars accelerate upon the mean Solar time for a month, 221. Of the first part of the Equation of time, 229; of the second part, 241. Of the precession of the Equinox, 247. Of the length of Sidereal, Julian, and Tropical Years, 251. Of the Sun’s place and Anomaly, following 251. Of the Equation of natural Days, following 251 Of the Conjunctions of the hour and minute hands of a Watch, 264. Of the Curves described by the Satellites, 272. Of the difference of time in the Moon’s rising and setting on the parallel of _London_ every day during her course round the Ecliptic, 277. Of Eclipses, 327. For calculating New and Full Moons and Eclipses, following 390. Of the Constellations and number of the Stars, 399. Of the _Jewish_, _Egyptian_, _Arabic_, and _Grecian_ months, 415. For inserting the Golden Numbers right in the Calendar, 423. Of the times of all the New Moons for 76 years, 424. Of remarkable Æras or Events, 433. Of the Golden Number, Number of Direction, Dominical Letter and Days of the Months, following 433.

THALES’s Eclipse, 323.

THUCYDIDES’s Eclipse 324.

_Tides_, their Cause and Phenomena, 295-311.

_Tide-Dial_ described, 441.

_Trajectorium Lunare_ described, 440.

_Tropics_, 198.

_Twilight_, none in the Moon, 254.

_Tychonic System_ absurd, 97.

U.

_Universe_, the Work of Almighty Power, 5, 161.

_Up_ and _down_, only relative terms, 122.

_Upper_ or _under side of the Earth_ no such thing, 123.

V.

_Velocity of Light_ compared with the velocity of the Earth in it’s annual Orbit, 197.

_Venus_, her bulk, distance, period, length of days and nights, 26. Shines not by her own light, _ib._ Is our morning and evening Star, 28. Her Axis, how situated, 29. Her surprising Phenomena, 29-43. The inclination of her Orbit, 45. When she will be seen on the Sun, _ib._ How it may probably be soon known if she has a Satellite, 46. Appears in all the Shapes of the Moon, 23, 141. An experiment to shew her phases and apparent motion, 141.

_Vision_, how caused, 167.

W.

_Weather_, not hottest when the Sun is nearest to us, and why, 205.

_Weight_, the cause of it, 122.

_World_ not eternal, 164.

Y.

_Year_, 407, Great, 251, Tropical, 408, Sidereal, 400, Lunar, 410, Civil, 411, Bissextile, _ib._ _Roman_, 413, _Jewish_, _Egyptian_, _Arabic_, and _Grecian_, 415, how long it would be if the Sun moved round the Earth, 111.

Z.

_Zodiac_, what, 397. How divided by the antients, 398.

_Zones_, what, 199.

DIRECTIONS to the BOOKBINDER.

The ORRERY PLATE is to front the Title Page.

PLATE I fronting Page 5 II 39 III 49 IV 73 V 81 VI 97 VII 125 VIII 147 IX 147 X 157 XI 179 XII 203 XIII 279

Footnotes

Footnote 1:

Dr. YOUNG’s Night Thoughts.

Footnote 2: