Made usE of in 'Astronomy. 41.5.

dian with them; or it is the time the fun rises or letsbefore or after six o’clock. •

Atmosphere, that collection of vapours, or body of air,which surrounds ot encompasses the earth.

Attraction, a property of matter, by which bodies aremade to approach towards each other, without any sen-sible agent either drawing or impelling them.

Aurora, the morning twilight, which begins to appearwhen the fun is about eighteen degrees below thehorizon.

Auriga, a northern constellation containing forty-sixstars.

Axis of the earth, or of a planet, an imaginary linepassing through the center from one pole to the other;or that round which they are supposed to perform theirdiurnal rotations.

Azimuths, great circles which pass through the zenithand nadir, and are perpendicular to the horizon.—TheAzimuth of any celestial object is an arc of the horizon,contained between the east or west point of the heavens,and a vertical circle passing through the center of thatobject.

B.

Basilicus, or Cor Leonis, a fixed star of the first mag-nitude in the constellation Leo.

Bears, two constellations in the northern hemisphere,called Ursa Major and Ursa Minor; the first consistingof one hundred and five stars, and the second of twelve:The north pole star is in the tail of the little Bear.

Berenices Hair, a northern constellation consisting oftwenty-four stars.

Betelguese, a star of the second magnitude in the eastshoulder... of Orion.

Bissex-