ORI 



ORT 



monia and alf, owing to the formation of 

 orcein. 



O'RDINATE {ordino, to arrange). A 

 term applied, in Conic Sections, to one 

 half of any line drawn across an ellipse, 

 parallel to the minor axis. The whole 

 line is called a double ordinate, and the 

 portion of the major axis which it cuts 

 off is called an abscissa. These terms 

 are equally and similarly applicable to 

 the parabola and the hyperbola. 



ORES. The mineral bodies from 

 which metals are extracted. These are 

 termed sulphurets, when combined with 

 sulphur; oxides, when combined with oxy- 

 gen ; and salts, when combined with acids. 



ORGA'NIC REMAINS (o'pvavoi/, an 

 organ). The remains of organized bodies, 

 both plants and animals, found in a fossil 

 state. 



ORGANO'GRAPHY (op-yai/ov, an 

 organ, ypd^xa, to describe). By this term 

 De Candolle designated his learned 

 work on the structure of plants; and 

 although the word simply means a "de- 

 scription of organs," it has been restricted 

 to the organs of plants, comprising an 

 account of their elementary tissues, and 

 of their compound structures. 



O'RGANON (opYavoi/, an instrument 

 or machine). A philosophical term, de- 

 noting a method, and usually applied to 

 a body of rules and laws for conducting 

 a scientific inquiry. What is called the 

 Organon of Aristotle, is a collection of 

 the views of that philosopher on the 

 several subjects of the Categories, includ- 

 ing his Logic ; of the Interpretation or 

 the Nature of Propositions ; of the 

 former and latter Analytics ; of Topics ; 

 and of Sophisms. The term organon 

 was not given by Aristotle, but is of a 

 date posterior to him. 



Novum Organon Scientiarum. The 

 name given by Bacon to his learned work 

 on " A New Method of studying the 

 Sciences." This method, which is founded 

 on the principle of Induction, or actual 

 experiment, which Bacon significantly 

 terms "Asking Questions of Nature," 

 has earned for its author the appellations 

 of the Prophet of the Arts and the Father 

 of Experimental Philosophy. See Baco- 

 nian Philnsophy . 



ORIOLl'NiE {oriolus, the oriole). 

 Orioline birds, or Orioles ; a family of 

 the Cantatrices o{ Macgillivray, belonging 

 to the warmer regions of the Old Con- 

 tinent. They appear to be allied to the 

 Rollers, not only in the form of the bill, 

 but also in their short tarsi and broad toes. 

 243 



ORI'ON. A southern constellation, 

 consisting of seventy-eight stars, the 

 principal of which is Betelgeuse. 



ORNITHO'LOGY {6'pviv, a bird, \6- 

 70P, an account). The science which 

 teaches the natural history and arrange- 

 ment of birds. See Zoology. 



O 'RP IMENT (auri pigmentum). A ge- 

 neral name for two sulphurets of arsenic, 

 the yellow, or prismatoidal sulphur, and 

 the red, ruby sulphur, or hemi-prismatic 

 sulphur. The former is the colouring 

 principle of the paint called King's yellow. 



O'RRERY. A machine for repre- 

 senting the motions, relative magnitudes, 

 and distances of the bodies composing 

 the solar system ; said to have been 

 named after an earl of Orrery, for whom 

 the first machine of the kind was made 

 by Prince Eugene. Planetary machines 

 have received various names, sulficiently 

 indicative of their object, viz., planeta- 

 rium, tellurian, lunarian, and satellite 

 machine. 



ORSEDEW. Manheim or Dutch Gold ; 

 an inferior sort of gold leaf, prepared of 

 copper and zinc, sometimes called leaf 

 brass, and principally manufactured at 

 Manheim. 



O'RTHITE {opOof, upright). A sili- 

 cate containing yttria and protoxide of 

 cerium, and named from its always oc- 

 curring in straight layers, generally in 

 felspar. 



ORTHOCERA'TA (op^op, straight, 

 K€pai, a horn). An extinct genus of 

 Cephalopods, which inhabited a long- 

 chambered conical shell, like a straight 

 horn. 



ORTHOGO'NAL {hpOo^, right, ytavia, 

 an angle). In Geometry, this term simply 

 means at right angles, or perpendicular • 

 thus, a curve cuts a set of curves ortho- 

 gonally, when it cuts them all at right 

 angles. The term is sometimes used 

 synonymously with orthographic, and 

 relates to a particular mode of projection. 

 See Projection. 



ORTHO'GRAPHY (hpOof, right, ypd- 

 <p(a, to write). In its general sense, this 

 term denotes that part of Grammar which 

 teaches the nature and powers of letters, 

 and the correct method of spelling and 

 writing words. The sense of the word 

 has, however, been restricted by gram- 

 marians to the proper selection of the 

 letters of words, and the correct division 

 of words when separated by the termina- 

 tion of lines. 



ORTHO'PTERA (op^o?, straight, tttc- 

 p6i/, a wing). An order of insects, com* 

 M2 



