opal 
without crystalline structure : it usually con- 
tains some water, mostly from 3 to 9 per cent. 
There are many varieties, the chief of which are (a) pre- 
cious or noble opal (including the harlequin opal), which 
exhibits brilliant and changeable reflections of green, 
blue, yellow, and red, and which is highly valued as a gem ; 
(b) fire-opal, which affords an internal red fire-like reflec- 
tion ; (<) common opal, whose colors are white, green, 
yellow, and red, but without the play of colors (cacholong 
has a milk-white or bluish-white color, resembling porce- 
lain); (d) emf-opoi,thevarietiesofwhichare more opaque 
than common opal (here belong the jasp-opal or opal- 
jasper and most wood-opal) ; (e) hydrophane, which as- 
sumes a transparency only when thrown into water; (/) 
hyalite, which occurs in small globular and botryoidal 
forms, colorless and transparent, with a vitreous luster; 
(g) inenilite, which occurs in irregular or reniform masses, 
and is opaque or slightly translucent; (h) florite, sili- 
cious sinter, or geyserite, the form of silica deposited by 
hot springs and geysers; and (t) tripolite, or infusorial 
earth formed of the silicious shells of diatoms. Formerly 
the opal was believed to possess magical virtues, as the 
conferring of invisibility when wrapped in a bay-leaf. 
Now ... the tailor make thy doublet of changeable taf- 
feta, for thy mind is a very opal. Shak., T. N., ii 4. 77. 
Opal glass. Same as opalescent glass. Seeglass. Opal- 
glass slip, in a microscope, a piece of opal glass placed 
under the object upon the stage, to subdue or diffuse the 
light passing through the object. Opal plate, in photon., 
a plate of opal glass, whether prepared as a sensitized diy 
plate, or plain, or a celluloid film of a white color, used 
for making positives or porcelain pictures. Such a cellu- 
loid film is often called ivory film. 
opal-blue (6'pal-blo), n. Same as basic blue 
(which see, under blue). 
opaled (6'pald), a. [< opal + -ed z .'] Bendered 
iridescent like an opal. 
A wreath that twined each starry form around, 
And all the opal'd air in colour bound. 
Foe, Al Aaraaf, i. 
opalesce (6-pa-les'), v. i.; pret. and pp. opa- 
lesced, ppr. opalescing. [< opal + -esce.] To 
give forth a play of colors like the opal ; ex- 
hibit opalescence. [Bare.] 
opalescence (6-pa-les'ens), n. [< F. opales- 
cence; as opalescen(t) 4- -ce.~] The quality of 
being opalescent ; iridescence like that of the 
opal ; a play of colors milky rather than bril- 
liant; the property of exhibiting such a play 
of color. 
opalescent (6-pa-les'ent), a. [< F. opalescent; 
as opalesci 1 + -ent.] 1. Having variegated and 
changing colors like those of the opal. 2. 
Milky Opalescent glass. See glass. 
Opalina (o-pa-li'na), n. [NL., fern, of opalinus, 
opaline: see opaline.'] 1. The typical genus 
of Opalinida;. They are simply ciliate, without special 
prehensile organs and with no contractile vacuole. 0. 
ranarum swarms in the rectum of frogs. 
2. {1. c.~] A species of this genus. 
opaline (6'pa-lin), a. and n. [< F. opalin = Sp. 
Pg. It. opalino, < NL. opalinus, opaline, < L. opa- 
lus, opal: see opal.] I. a. Pertaining to or like 
opal ; also, like some property of the opal ; 
specifically, having an iridescence like that 
of the opal ; bluish-white, reflecting prismatic 
hues, as the wings of certain insects. 
II. . 1. A semi-translucent glass, whitened 
by the addition of phosphate of lime, peroxid 
of tin, or other ingredients. E. H. Knight. 
2. An opalina. 
Opalinidae(6-pa-lm'i-de),N.^. [NL.,< Opalina 
+ -fcte.] A family of holotrichous ciliated In- 
fusoria, typified by the genus Opalina, occur- 
ring as endoparasites within the rectum and in- 
testinal viscera of Amphibia and Invertebrate. 
opalinine (6'pa-lin-in), a. Pertaining to the 
Opalinidte, or having their characters. 
opalize (6'pa-liz), v. t.; pret. and pp. opalized, 
ppr. opalizing. [< opal + -ize.~} To cause to 
resemble opal or to assume its structure or 
appearance: as, opalized wood. Also spelled 
opalise. 
opal-jasper (6'pal-jas"per), n. Same us jasper- 
opal. 
opaloid (6'pa-loid), a. Semi-translucent. See 
opaline, n., 1. 
Each lamp being enclosed within a ground (glass) or 
opaloid shade. Dredge's Electric Illumination, I. 643. 
Opaque (o-pak'), a. and n. [Formerly also opake; 
< ME. opake, < OF. (and F.) opaque = Sp. Pg. 
It. opaco, < L. opacus, shaded, shady, darkened, 
obscure, such as to give or cast a shadow.] I. 
a. If. Shady; dark; hence, obscure. 
Thai honge hem uppe in place opake and drie. 
Palladius, Husbondrie (E. E. T. 8.), p. 53. 
2. Impervious to the rays of light ; not trans- 
parent. 
The purest glass and crystal quench some rays- the 
most armque metal, if thin enough, permits some rays to 
pass through it. Tyndall, Light and Elect., p. 13. 
3. In entom., having no luster: said of sur- 
faces or colors. 4. In hot., mostly used in the 
4118 
sense of 'not shining,' or 'dull.' Opaque china. 
(a) A name given to a fine pottery made at Swansea from 
about 1800. See Swansea porcelain, under porcelain, (b) 
A similar ware made at Spode, introduced in 1805. Also 
called feldspar porcelain and ironstone china. Opaque 
illuminator. See illuminator. 
II. n. Opacity. 
Thro' this opaque of nature and soul. 
Young, Night Thoughts, i. 43. 
opaque (o-pak'), . t. ; pret. and pp. opaqned, 
ppi.opaq'uiiig. [<. opaque, a.] To render opaque. 
What is the most simple, economical, and practical way 
of opaquing the backgrounds on negatives of furniture, 
so as to give prints showing only the object on the clear 
paper? Sci. Amer., N. S., LIX. 235. 
opaquely (o-pak'li), adv. In an opaque man- 
ner; darkly; dimly. 
opaqueness (o-pak'nes), n. The property of 
being opaque or impervious to light; opacity. 
opet (6p), a. [ME. ope, a reduced form of open : 
see open, a.] Open. 
He foune the gate wyde ope, and in he rode. 
Spenser, F. Q., VI. vi. 19. 
Tear down these blacks, cast ope the casements wide. 
Fletcher (and another), Queen of Corinth, iii. 2. 
ope (6p), f. t. and i. ; pret. and pp. oped, ppr. 
oping. [< ope. a. Cf. open, v.'] To open. [Now 
only archaic.] 
Before you fight the battle, ope this letter. 
Shak., Lear, v. 1. 40. 
opeidoscope (o-pi'do-skop), n. [Irreg. < Gr. 
oty (OTT-), voice, + eliof, form, + ammtlv, view.] 
An instrument for illustrating sound by means 
of light. It consists of a membrane upon which is a 
mirror. When the membrane is caused to vibrate by a 
sound, as that of the voice, the mirror exhibits this vibra- 
tion on a screen by means of the movements of a ray of 
light reflected from it. 
open (6'pn), a. and n. [< ME. open, opyn, rare- 
ly ope, <. AS. open = OS. opan, open = OFries. 
open, opin, epen = D. open = MLG. open, LG. 
open, open = OHG. ophan, ofan, offan, MHG. 
G. offen = Icel. opinn = Sw. oppen = Dan. aaben, 
open ; in form as if orig. pp. of a strong verb, 
AS. *upan, etc. (which does not appear), sup- 
posed to be < up, up; as if lit. ' lifted up,' as a 
tent-door, the lid of a box, etc. (cf . dup, orig. do 
up, open): see up."] I. a. 1. Unclosed, literally 
or figuratively ; not shut or closed ; hence, af- 
fording access, or free ingress and egress : as, 
an open door. 
On a sudden open fly 
With impetuous recoil and jarring sound 
The infernal doors. Milton, P. L., ii. 879. 
Wide open were his eyes, 
As though they looked to see life's mysteries 
Unfolded soon before them. 
W. Morris, Earthly Paradise, III. 321. 
(a) Unstopped : as, an open bottle, (b) Unsealed : as, an 
open letter, (c) Uncovered : as, an open jar ; an open drain. 
(d) Without deck : as, an open boat, (e) Without protect- 
ing barrier of any kind : as, an open harbor or roadstead ; 
an open gallery. (/) Exposed ; liable ; subject. 
I delighte not to laye open the blames of soe great Ma- 
gistrats to the rebuke of the woorlde. 
Spenser, State of Ireland. 
Lay but to my revenge their persons open. 
Fletcher, Wildgoose Chase, iii. 1. 
The whole country lay open to inroads. 
Irving, Granada, p. 83. 
(g) Free from or without physical hindrance or impedi- 
ment ; clear ; hence, free of access ; affording free passage : 
as, the river is now open for navigation. 
Choose out a gift from seas, or earth, or skies, 
For open to your wish all nature lies. 
Addison, tr. of Ovid's Metamorph., ii. 
(A) Unfilled; unoccupied: as, the appointment is still 
open, (i) Undecided; unsettled or undetermined: as, an 
open question, (j) Not yet balanced or adjusted ; not yet 
closed or wound up; subject to further additions : as, an 
open account or policy. (*) At liberty ; free ; as yet disen- 
gaged; not preoccupied or prepossessed ; not forestalled; 
available : as, an open day ; open to engagements. (I) Pre- 
senting no moral or logical hindrance or difficulty ; mor- 
ally or logically possible. 
O, were it only open yet to choose 
One little time more whether I'd be free 
Your foe, or subsidized your friend forsooth ! 
Browning, Ring and Book, II. 258. 
Of course, it is open to the creationist to say that no act 
of creation has taken place since man was called into being. 
Pop. Sci. Mo., XXXI. 35. 
(m) Unrestricted; public; free to be used or enjoyed by 
all : as, open market ; open competition. 
If Demetrius, and the craftsmen which are with him, 
have a matter against any man, the law is open. 
Acts xix. 38. 
As she hath 
Been publicly accused, so shall she have 
A just and open trial. Shak., W. T., ii. 3. 205. 
Hee then presently gaue licenses to all the Vintners to 
keepe open house. Delcker, Seven Deadly Sins, p. 32. 
2. Uninclosed ; not inclosed or surrounded by 
barriers; accessible on all or nearly all sides; 
affording free ingress or access on all sides or 
open 
on more sides than one : as, the open country ; 
an open space; the open sea. 
In open places stand 
Their crosses vnto which they crooche, and blesse them- 
selues with hand. Uakluyt's Voyagee, 1. 385. 
We are in open field ; 
Arming my battles, I will tight with thee. 
Greene, James IV., v. 
Hence (a) Not shut off or obstructed; unobstructed; 
free ; clear : as, the open air ; an open view ; open day. 
Fowl that may fly above the earth in the open firmament 
of heaven. Gen. i. 20. 
Dreaming by night under the open sky. 
Milton, P. L., iii. 514. 
(6) Not obstructed by ice or frost ; clear of ice ; as, open 
water in the polar seas ; hence, as applied to weather or 
the seasons, not marked by ice and snow ; mild ; moder- 
ate : as, open weather. 
Did you ever see so open a winter in England? Swift. 
3. Not drawn, folded, or rolled together; un- 
closed; unfolded; expanded; spread out: part- 
ed ; apart : as, an open hand ; an open flower ; 
in open order. 
He had in his hand a little book open. Rev. Jt. 2. 
I saw a smith stand with his hammer, thus, 
The whilst his iron did on the anvil cool, 
With open mouth swallowing a tailor's news. 
Shak., K. John, iv. 2. 195. 
I tried on my riding-cloth suit with close knees, the first 
that ever I had ; and I think they will be very convenient, 
if not too hot to wear any other open knees after them. 
Pepyi, Diary, June 12, 1662. 
Hence 4. Free in giving or communicating; 
liberal; generous; bounteous. 
His heart and hand both open, and both free ; 
For what he has he gives ; what thinks, he shows. 
Shak., T. and C., iv. 5. 100. 
5. Containing apertures ; perforated ; of a loose 
texture : as, open work. 
The following varieties of open red woods are used to a 
greater or less extent [in dyeing]. 
W. Crookes, Dyeing and Calico-printing, p. 331. 
6. Not concealed ; plain in the sight of all ; ex- 
posed to view: as, open shame. 
Some men's sins are open beforehand, going before to 
judgment. 1 Tim. v. 24. 
7. Free from concealment, dissimulation, re- 
serve, or disguise ; not secret or secretive ; plain 
and aboveboard; candid; frank; free-spoken; 
ingenuous : as, an open face ; an open avowal ; 
an open enemy ; open defiance. 
Come, you are a strange open man, to tell everything 
thus. B. Jonton, Epicosne, i. 1. 
Tom struts a soldier, open, bold, and brave. 
Pope, Moral Essays, i. 153. 
Be explicit, be open in the most unbounded manner, and 
deal like a man of sense. Walpole, Letters, II. 432. 
The great lords 
Banded, and so brake out in open war. 
Tennyson, Coming of Arthur. 
8. Beady (to hear, do, see, or receive anything) ; 
attentive ; receptive ; amenable, as to reason, 
advice, influence, pity, etc. 
The eyes of the Lord are upon the righteous, and his 
ears are open unto their cry. Ps. xxxiv. 15. 
Ferdinand, though far from vindictive, was less open to 
pity than the queen. Prescott, Ferd. and Isa. , ii. 7. 
9. In music. See open diapason, open linrmony, 
open string, etc., under the nouns. 10. Uttered 
with an unclosed or a less closed position of the 
mouth-organs: as, a sibilant is a more open 
sound than a mute ; a vowel is more open than 
a consonant ; open and close e. 11. Not closed 
by a consonant : said of a vowel, or a syllable 
ending in a vowel, upon which another vowel 
follows. 
These equal syllables alone require, 
Though oft the ear the open vowels tire. 
Pope, Essay on Criticism, 1. 345. 
12. In elect., not forming a part of a closed 
circuit ; not connected with other wires or with 
the earth so as to form a complete electric cir- 
cuit. 13. In chemical and other industries, a 
term applied to steam admitted directly into a 
tank or vessel, and acting directly upon sub- 
stances to be treated, as fabrics or yarns in 
dyeing, or materials in soap-making. Also called 
wet-steam, because as soon as admitted it begins to con- 
dense, and thus always holds in suspension a consider- 
able percentage of water. Letters of open doors, in 
Scots Joii', letters passing the signet, which are requisite 
where goods are to be poinded which are deposited in 
lockfast places Open account. See account current, 
under account. - Open battery, bead-sight, charter, 
communion. See the nouns. Open circuit, in elect. 
See circuit, 12. Open contract. See contract. Open 
credit. See credit. Open crown, (a) A crown without 
the arched-over or partly closed top, which form, in mod- 
ern heraldry, is considered as essential to a crown of sov- 
ereignty ; hence, the crown of a personage of rank less 
than sovereign ; a coronet, (b) A badge or ornament re- 
sembling a coronet set upon the left shoulder or planted 
on the left breast of English effigies of the fifteenth and 
