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Chambers, Ephraim, 1680 (ca.)-1740 / Cyclopædia, or, An universal dictionary of arts and sciences : containing the definitions of the terms, and accounts of the things signify'd thereby, in the several arts, both liberal and mechanical, and the several sciences, human and divine : the figures, kinds, properties, productions, preparations, and uses, of things natural and artificial : the rise, progress, and state of things ecclesiastical, civil, military, and commercial : with the several systems, sects, opinions, &c : among philosophers, divines, mathematicians, physicians, antiquaries, criticks, &c : the whole intended as a course of antient and modern learning

Opprobrii - ozaena,   pp. 667-682 PDF (14.2 MB)

Page 667

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Edipfes of the Moon never happen but when fhe is in
Oppofizion with the Sun, and when they both meet in the
bLudes of the  c-liptic. See ECLIPSE. AMars in his Oppofi-
:ioxz tothe Sun, is nearer the Earth than he is to the Sun.
OPSONOMU    AS, in Antiquity, a 1agiftrate of Atbens,
whereof there were two, or three; chofien out of the Senate,
or Council. Their Office was to infpe& the Filh-Market,
and to take care that every thing were done in Order,
and according to the Laws.
OPTATIVE, in Grammar, the third Mood of the
Conjugations of Verbs, ferving to exprefs an ardent Defire
or'Wilh for any thing. See MOOD.
Inflead of a Varticular Mood, or a particular Set of In-
flexions to exprefs this Defire, the EngliJ', Latins, &c. ex-
prefs it by an Adverb of Wifhing prefix'd to it. The Latins
by Irtinamn the French by Pltu a Dieu; and the EngliJL by
Would to God, &c.
In thefe Languages, fetting afide the Adverb, the Op-
tative is the fame with the Subjunaive  the Inflexions of
the Verb, which make what we call the Moods, are the
fame in both.
Indeed, in the Greek, the With is exprefs'd by a par-
ticular Inflexion, thence call'd Optative ; and in the French,
Span.1k, and Italian, there is fomething like it ; their
triple Tenfes ferving the fame purpofes. But the Optative
Mood may be fafely retrench'd from the Latin and Engl/LJ.
OPTERIA, among the Antients, Prefents made to a
Child, the firil time a Perfon faw it.
The Word was alfo ufed for the Prefents which the
Bridegroom made his Bride when the was conduaed to
him; this being the firfi time he faw her. See Barthol.
de Puerp.Vret.
The Word isform'd from the Greek oo7vyoet, I fee.
OPTICS, is properly the Science of direct Vifion. See
Tbo', Sometimes, the Word is ufed in a larger Senfe for
the Science of Vifion, or Vifibles in general: In which
Senfeit includes Catoptrics, and Dioptrics; and even Per-
fpeaive. See CAToP'RICs, DIOPT RICS, and PERSPEC-
Optics in its more extenfive Acceptation, is a mix'd Ma-
thematical Science, which explains the manner wherein
Vifion is perform'd in the Eye ; treats of Sight in the ge-
neral ; gives the Reafons of the feveral Modifications or
Alterations which the Rays of Light undergo in the Eye;
and Ihews why Objeffs appear fometimes greater, fome-
times fmaller, fometimes more diflind, fometimes more
confufed, fometimes nearer, Sometimes more remote. See
In thisextenfive Signification, it is confider'd by Sir if.
Newton in his admirable Work call'd Optics.
Optics makes a confiderable Branch of Natural Philofo-
phy j both as it explains the Laws of Nature, according to
which Vifion is perform'd 3 and as it accounts for abun.
dance of Phyfical Phenomena, otherwife inexplicable.
For what can be determined about Light, Colours, Tranf-
parency, Opacity, Brightnefs, Meteors, the Rainbow,
Farrhelia, ec. but on Principles of Optics?  What about
the Nature of the Stars ? The Strucure of the Mundane
Syflem ? The Motions of the Planets ? The Eclipfes of
the Luminaries ? Wc.
Optics, therefore, make a confiderable Part of Atro-
nomy. See ASTRONOMY.
From Optics likewife arifes Perfpeffive ; all the Rules
whereof have their Reafon or Foundation in Optics. Indeed
Tacquet makes Perfpeffive a part of Optics; tho'jobn Arch-
bilhop of Canterbury, in his Perfpefiva Communis, cal Is op-
tics, Catoptrics, and Dioptrics by the Name Perfpedive.
Euclid has wrote on the andent Optics and Catoptrics:
Dioprtrics were unknown to them. F. Honorat. Fabri has an
Abridgment of Optics, Catoptrics, and Dioptrics. Father
Efcbinard a Century of Problems in Optics. Vitellio, and
Ahbazon have done well on the PrincIples of Optics. Father
Kircher has a large Volume on the Secrets of Optics, of
Light, and Shadow ; and its furprizing Effeas, which
pafs on the People for Magic. We have alfo l"Optique &
Catoptriqye of F. Merfenne, Paris I65i. Dioptrique Oculaire
of Fath. Cberubin, Paris 167 I, Fol. Cbrift. Scbeineri Optica,
Loend. i6z. 2 Jacobi Gregorii Optica, Lond. x663. Sob. Bap.
Yorti de Refralione Optices. Barrovii Lelffones Optice, Lond.
i669. Principe Generale de l'Optique, by Mr. Leibnitz, in
the Leip;c Aes, I682. L'Occ"iale all' Occbio, or Dioptrica
Traffica, Carol. Ant. Mancini, Boulogne x66o, 4. Pkf'co-
Mathefi, de Lumine, Coloribrls f Iridi, per F. Mar. Grimaldi,
Bononie i665, 40. CogitatiOnes Pbyfico-Mecbanict de Natura
Iiffonts, per goban. Ott. Scaphufam, Heidel. i670, 40. And,
who ought to have been named firff, the great Sir I. Newton,
in his Optics, Engli/j and Latin, 4Q.
OPTIC-Nerver, the fecond Pair of Nerves, fpringing from
the Crura of the Medula Obloygara, and pafing thence to the
Eye. See NERVE.
Thefe Nerves approach, by degrees, in their recefs from
their Origin; and at length nieet, in the Bafis of the
Brain, near the Infundibulum. Thence they again fepa.
rate, but without decuffating  and proceed, one to each
Eye.  See EY E.
They are cover'd with two Coats, which they take from
the Dura and Pia Mater; and which, by their Expanfions,
form the two Membranes of the Eye, call'd the lvea and
Cornea. See Uv E A, l$C.
The Retina, which is a third Membrane, and the imme-
diate Organ of Sight, is only an Expanfion of the fibrous,
or inner, and medullary Part of thefe Nerves. Sze RE-
The Conflruffion of the Optic-Nerve feems to be different
from that of the other Nerves, which all appear to confift
of hard Fibres: For this, e'er it enters the Orbit of the
Eye, is only a Coat or Cover form'd by the Pia Mater, and
including a Produffion of the Medalla of the Brain; which
is eafily feparated from it. At its entrance into the Eye,
it takes another Coat from the Dura Mater; which two
Coats are bound together by exceedingly fine Filaments:
That from the Pia Mater is continued in the Ctoroides, and
that from the Dura Mater in the Uvea.
From their Entrance within the Orbit, to the Ball of
the Eye, the Medulla, enclofed under the two Coats, is fe-
parated into a number of little Cells anfwering to each
other. See VISION.
OPTIc-Pencil, or Pencil of Rays, is that Affemblage of
Rays by means whereof any Point or Part of an Objec& is
feen. See PENCIL and RADIANT.
Some Optic Writers laugh at the Notion of Optic-Pencils,
and maintain 'em mere Chimera's.
OPTIc-Pyramid, in Perfpeclive, is the Pyramid A BCO
(Tab. PERSPECTIVE, Fig. 12.) whofe Bafe is the vifible
Objed A B C; and its Vertex, in the Eye 0; form'd by
Rays drawn from the feveral Points of the Perimeter to
the Eye.
Hence alfo appears, what is meant by Optic Triangle.
OPTIC Rays, are particularly ufed for thofe wherewith
an Optic-Pyramid, or Optic-Triangle, is terminated 3 as 0 A,
O C, O B.
OPT IC Axis, is a Ray paffing through the Centre of the
Eye; or the middle of the Optic-Pyramid, &c.
OPTIC Chamber, fee Camera OBSCURA.
OPTIc-Glaffes, are Glaflfes ground either concave, or
convex, fo as either to colle&, or difperfe the Rays of
Light; by means whereof Vifion is improved, and the
Eye firengthned, preferved,&c.
For the manner of Grinding and Polifhing Optic-Gla/Jes,
For their Phenomena, fee LENs, MIRROR, FC.
The Principal among Optic-Gh~l/es, are Telfcopes, Micro-
fcopes, Spe-Racles, Readinp-Glaqfs, Magic Lanpborns,&c. See
the Contdruaion and Ufe of each under its proper Article,
horn, &c.
OPTIC Place of a Star, &ec. is that Point of its Orbit in
which it appears tobe, to our Eye. See PLACE.
This iseither true j as when the Eye is fuppofed ft the
Centre of the Earth, or Planet it inhabits ; or apparent, as
when at the Circumference. See APPARENT, PLANET,
The difference between the two, is the ParaTlax. See
OPTICAL Inequality, in Afironorny, is an apparent Tr-
regularity in the Motions of far difiant Bodits; fo call'd,
becaufe not really in the moving Bodies, but arifing from
the Situation of the Spefator's Eye : So that were the
Eye in the Centre, it would always fee the Motions uni-
The Optical Inequality may be thus illuflrated: Suppofea
Body revolving in the Periphery of a Circle A B D E F GQ,
(Tab. OPTICS, Fibg. 40.)  and moving through equal
Arches AB, BD, DE, EF, in equal Times; and fuppofe
the Eye in the Plane of the fame Circle, but at a diflance
from it, viewing the Motion of the Bodv from 0: When
the Body goes from A to B; its apparent Motion is mea-
fured by the A ngle A O B, or the Arch H L, which it will
feem to defcribe. But in an equal time, while it moves
thro' the Arch B D, its apparent Motion will be determi-
ned by the Angle B 0 D, or the Arch L M, which is lefs
than the former Arch H L. And when arrived at D, it
will be feen at the Point M of the Line N L M. But it
fpends the fame time in defcribing D E, which is equal to
A B or B D ; and when arrived at E, is fill feen at M;
appearing Stationary in all the Space from D to E. When
it arrives at E, the Eye- will fee it in L; and at, G, will
appear at H; fo that it will feem to have gone retrograde:
And, laftly, from Q to P, it will again appear Statio-
nary.                                        OPTI_

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