- 1Letter I — Introductory Observations
- 2Letter II — Doctrine of the Sphere
- 3Letter III — Astronomical Instruments — Telescope
- 4Letter IV — Telescope Continued
- 5Letter V — Observatories
- 6Letter VI — Time and the Calendar
- 7Letter VII — Figure of the Earth
- 8Letter VIII — Diurnal Revolutions
- 9Letter IX — Parallax and Refraction
- 10Letter X — The Sun
- 11Letter XI — Annual Revolution — Seasons
- 12Letter XII — Laws of Motion
- 13Letter XIII — Terrestrial Gravity
- 14Letter XIV — Sir Isaac Newton — Universal Gravitation — Figure of t…
- 15Letter XV — The Moon
- 16Letter XVI — The Moon — Phases — Harvest Moon — Librations
- 17Letter XVII — Moon’s Orbit — Her Irregularities
- 18Letter XVIII — Eclipses
- 19Letter XIX — Longitude — Tides
- 20Letter XX — Planets — Mercury and Venus
- 21Letter XXI — Superior Planets: Mars, Jupiter, Saturn, and Uranus
- 22Letter XXII — Copernicus — Galileo
- 23Letter XXIII — Saturn — Uranus — Asteroids
- 24Letter XXIV — The Planetary Motions — Kepler’s Laws — Kepler
- 25Letter XXV — Comets
- 26Letter XXVI — Comets, Continued
- 27Letter XXVII — Meteoric Showers
- 28Letter XXVIII — Fixed Stars
- 29Letter XXIX — Fixed Stars Continued
- 30Letter XXX — System of the World
- 31Letter XXXI — Natural Theology
- 32Letter XXXII — Recent Discoveries
- 33Recent Discoveries
Letters on Astronomy
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