COMETARIUM

, a machine adapted to give a representation of the revolution of a comet about the sun. | It is so contrived as, by elliptical wheels, to shew the unequal motion of a comet in every part of its orbit. The comet is represented by a small brass ball, carried by a radius vector, or wire, in an elliptical groove about the sun in one of its foci; and the years of its period are shewn by an index moving with an equable motion over a graduated silvered circle. See a particular description, with a figure of it, in Ferguson's Astron. 8vo. pa. 400.