HIP-KNOB, in architecture, the finial on the hip of a roof, between the barge-boards of a gable. HIPPARCHUS (fl. 146-126 B.C.), Greek astronomer, was born at Nicaea in Bithynia early in the 2nd century B.C. He observed in the island of Rhodes probably from 161, certainly from 146 until about 126 B.C., and made the capital discovery of the precession of the equinoxes in 130 (see ASTRONOMY: _History_). The outburst of a new star in 134 B.C. is stated by Pliny (_Hist. nat._ ii. 26) to have prompted the preparation of his catalogue of 1080 stars, substantially embodied in Ptolemy's _Almagest_. Hipparchus founded trigonometry, and compiled the first table of chords. Scientific geography originated with his invention of the method of fixing terrestrial positions by circles of latitude and longitude. There can be little doubt that the fundamental part of his astronomical knowledge was derived from Chaldaea. None of his many works has survived except a Commentary on the _Phaenomena_ of Aratus and Eudoxus, published by P. Victorius at Florence in 1567, and included by D. Petavius in his _Uranologium_ (Paris, 1630). A new edition was published by Carolus Manitius (Leipzig, 1894). See J. B. J. Delambre, _Histoire de l'astronomie ancienne_, i. 173; P. Tannery, _Recherches sur l'histoire de l'astr. ancienne_, p. 130; A. Berry, _Hist. of Astronomy_, pp. 40-61; M. Marie, _Hist. des sciences_, i. 207; G. Cornewall Lewis, _Astronomy of the Ancients_, p. 207; R. Grant, _Hist. of Phys. Astronomy_, pp. 318, 437; F. Boll, _Sphaera_, p. 61 (Leipzig, 1903); R. Wolf, _Geschichte der Astronomie_, p. 45; J. F. Montucla, _Hist. des mathematiques_, t. i. p. 257; J. A. Schmidt, _Variorum philosophicorum decas_, cap. i. (Jenae, 1691). (A. M. C.) HIPPASUS OF METAPONTUM, Pythagorean philosopher, was one of the earliest of the disciples of Pythagoras. He is mentioned both by Diogenes Laertius and by Iamblichus, but nothing is known of his life. Diogenes says that he left no writings, but other authorities make him the author of a [Greek: mystikos logos] directed against the Pythagoreans. According to Aristotle (_Metaphysica_, i. 3), he was an adherent of the Heraclitean fire-doctrine, whereas the Pythagoreans maintained the theory that number is the principle of everything. He seems to have regarded the soul as composed of igneous matter, and so approximates the orthodox Pythagorean doctrine of the central fire, or Hestia, to the more detailed theories of Heraclitus. In spite of this divergence, Hippasus is always regarded as a Pythagorean. See Diogenes viii. 84; Brandis, _History of Greek and Roman Philosophy_; also PYTHAGORAS.