in Astronomy, a term applied to the rising and setting of the stars; or, more strictly speaking, to their emergence out of and immersion into the rays and superior splendor of the sun.—A star is said to rise heliacally, when, after having been in conjunction with the sun, and on that account invisible, it comes to be at such a distance from him as to be seen in the morning before sunrise; the sun, by his apparent motion, receding from the star towards the east. On the contrary, the heliacal setting is when the sun approaches so near a star as to hide it with his beams, which prevent the fainter light of the star from being perceived; so that the terms apparition and occultation would be more proper than rising and setting.

HELianthus, the GREAT SUNFLOWER; a genus of plants belonging to the syngenesia clas; and in the natural method ranking under the 49th order, Compositæ. See BOTANY Index.