in Geometry, a spiral line. See SPIRAL.—The word is Greek, ἕλιξ, and literally signifies "a wreath or winding;" of ἐλέων, involvo, "I environ."

In architecture, some authors make a difference between the helix and the spiral. A staircase, according to Daviler, is in a helix, or is helical, when the stairs or steps wind round a cylindrical newel; whereas the spiral winds round a cone, and is continually approaching nearer and nearer its axis.

Helix is also applied, in Architecture, to the caulicles or little volutes under the flowers of the Corinthian capital; called also urilles.

Anatomy, is the whole circuit or extent of the auricle or border of the ear outwards. In opposition to which, the inner protuberance surrounded thereby, and answering thereto, is called anthelix. See ANATOMY, No 141.

Snail, a genus of shell-fish belonging to the order of vermes testacea. See CONCHOLOGY Index.