By observing the eclipses of Jupiter’s satellites, it was first discovered that light is not propogated instantaneously, though it moves with an incredible swiftness: For if light came to us in an instant, an observer in T will see an eclipse of one of the satellites, at the same time that another in K would. But it has been found by observations, that when the Earth is in K, at her nearest distance from Jupiter, these eclipses happen much sooner than when she is in T. Now having the difference of time betwixt these appearances in K and T, we may find the length of time the light takes in passing from K to T, which space is equal to the diameter of the Earth’s annual orb. By these kinds of observations it has been found, that light reaches from the Sun to us in the space of eleven minutes of time, which is at least at the rate of 100,000 miles in a second.

FINIS.

AN INDEX OF THE
Astronomical Terms
Made Use of in this BOOK.

Acronical Rising and Setting of the Stars  Page [96]
Almacanthers[63]
Altitudes[ib.]
——— Meridian Altitude[63]
Amplitude[62]
Amphiscians[91]
Annual Motion[7]
Antœci[92]
Antarctic Circle[53]
——— Pole[ib.]
Antipodes[93]
Arctic Circle[52]
Arctic Pole[53]
Ascension[68]
——— Right[ib.]
——— Oblique[69]
Ascensional Difference[ib.]
Ascians[91]
——— Heteroscians[ib.]
Asterisms[36]
Atmosphere[81]
Axis[43]
——— of the World[49]
Azimuth[61]
Babylonish Hours[71]
Bissextile[78]
Circle[42]
——— Great Circles[ib.]
——— Parallel, or lesser Circles[43]
——— Secondary Circles[ib.]
Circles of the Sphere[47]
Climates[93]
Colures[53]
——— Equinoctial Colure[ib.]
——— Solstitial Colure[54]
Comets[29]
Conjunction[11], [207]
Constellations[36]
Cosmical rising and setting of the Stars[96]
Crepusculum[83]
Day, Natural and Artificial[69]
Declination[52]
Diurnal Motion7
Diurnal Arch[68]
Eclipses[208]
——— Solar[ib.]
——— Lunar[ib.]
Eclipses of Jupiter’s Satellites[212]
Ecliptic[53]
Egyptian Year[75]
Elongation[18]
Equator, or Equinoctial[48]
Equinoctial Points[53]
——— Precession of[55]
——— Vernal and Autumnal[70]
Excentricity[4]
Galaxy, or Milky Way[38]
Geocentric Place[19]
Globe[42]
——— Terrestrial[43]
——— Celestial[44]
Gregorian Account[80]
Heliacal rising and setting of the Stars[96]
Heliocentric Place[19]
Hemisphere[42]
——— Northern and Southern[49]
Heteroscians[91]
Horizon[58]
——— Sensible[ib.]
——— Rational[59]
Hour Circles[50]
Italian Hours[72]
Jewish Hours[ib.]
Julian Account[79]
Latitude, in Astronomy[56]
——— in Geography[84]
Longitude in Astronomy[56]
——— in Geography[87]
Meridian[50], [61]
Nadir[61]
Nodes[3], [202]
Nocturnal Arch[68]
Orbit[3]
Parallel of the Earth’s Semidiameter[23]
——— of the Earth’s Annual Orb[20]
Periœci[92]
Periscians[91]
Periodical Month[74], [202]
Phases of the Moon[201]
Planets[1]
——— Inferior and Superior[14]
Planetary Hours[72]
Poles[42]
——— of the World[49]
——— of the Ecliptic[56]
Polar Circles[52]
Points of the Compass[60]
——— Cardinal Points[59]
Primary Planets[5]
Retrograde Motion of the Planets[187]
——— of the Nodes[202]
Secondary Planets[5]
Sidereal Year[74]
Signs of the Zodiac[54]
——— Northern and Southern[ib.]
Solstices[71]
——— Summer and Winter Solstices[ib.]
Solstitial Points[53]
Sphere[42]
——— Parallel and Right[67]
——— Oblique[68]
Stationary[186]
Style Old[79]
——— New Style[80]
Synodical Month[74], [202]
Tropics (of Cancer and Capricorn)[52]
Twilights[83]
Vertical Circles[61]
——— Prime Vertical[62]
Zenith[61]
Zenith Distance[63]
Zones, Torrid, Temperate, and Frigid[90]

THE END

Directions to the Binder.

The great Orrery to face the Title. 
Plate I.Page 2
Plate II.28
The Globes35
Plate III.194
Plate IV.200
Plate V.214