The description and use of a new portable orrery, on a most simple construction, representing in two parts-the motions, and phn̆omena of the planetary system : But more particularly the motions of the earth and moon, round the sun, from whence the nature and causes of the vicissitudes of the seasons, days, and nights, solar and lunar eclipses, &c. are clearly explained. To which is prefixed, a short account of the solar system, or the true system of the world. The third edition, enlarged, with an account of the new discovered planet, called the Georgium Sidus, the return of the Comet whose appearance is shortly to be expected, and embelished with two new copper plates. By William Jones, mathematical instrument maker.