-ism 
of persons and designating theories, as !<>- 
tliiiininiii, I'nnilixiH, Hiiririiiiniii, etc., or theories 
associated with practice', especially in words 
of temporary use, us I'u'.ntrixm, .liirksiiiiixm, 
(Iran/ism, etc., siidi temporary wonls being 
formed as occasion requires, in unlimited num- 
bers. Such words are usually accompanied by 
a noun of the agent in -i.it, and an adj. in -ixlii; 
and often by a verb in -ise. See these suffixes. 
Ismailian,Ismaelian(is-ma-il'i-an, -el'i-an),. 
[< Imiinil, Ixiiiitfl (see def.), + -tan.'] A member 
of a sect of Shiite Mohammedans who main- 
tained that Ismail was the seventh and last of 
the true imams, and that their chief was his 
vicegerent on earth. Their doctrines, like those of 
their existing representatives, the Druses and Angara of 
Syria, departed widely from orthodox Mohammedanism, 
and were made known in detail only to the initiated. 
The Ismallians founded the Fatlmlte dynasty of Egypt 
and Syria (see t'atimitr'h and the sect of Assassins was an 
offshoot from them. 
Ismailism, Ismaelism (is'ma-il-izm, -el-izm), 
a. [< Jxiiiiiil. Ixutiii'l, + -ism.'] The doctrinal 
system of tho Ismailians. 
Under the Fatlmite Caliph Hakim, a new religion sprang 
out of Ismailixin, that of the Druses, so called from its in- 
ventor, a certain Uarazl or Dorzi. Jincyc. Brit, XVI. 594. 
Ismailite, Ismaelite (is'ma-il-It, -el-it), n. [< 
luiitail, Ismael, + -ite&.] Same as Ismailian. 
Ismailitic, Ismaelitic(is*'ma-i-Ht'ik, -el-it'ik), 
a. [< Ismailite, Ismaelite, + -ic.] Pertaining to 
Ismailism. 
The eminent men who revealed to the poet In Cairo the 
secrets of the Isma'iKKc faith. Encyc. Brit., XVII. 238. 
ismatic (iz-mat'ik), a. [< ism + -atic 2 .] Per- 
taining to isms or an ism ; addicted to isms or 
theories. [Bare.] 
ismatical (iz-mat'i-kal), a. [< ismatic + -a/.] 
Same as ismatic. [Bare.] 
ismaticalness (iz-mat'i-kal-nes), . The qual- 
ity of being addicted to isms or theories. 
[Bare.] 
The Ism is the difficulty. This governs their action ; 
this they would thrust upon us. Their Iftmaticaljuws con- 
ceals and extrudes the Christian. S. Judd, Margaret, iii. 
iso-. [L., etc., iso-, < Gr. loo-, combining form 
of I'roc, Attic Z<rof, Epic also Finos, equal, the 
same (in number, size, appearance, etc.), like.] 
An element in some words of Greek origin, 
meaning 'equal.' 
isoabnormal (i'so-ab-nor'mal), n. [< Gr. iffof, 
equal, + E. abnormal.'] A line, either imagina- 
ry or drawn on a map of any part of the earth's 
surface, connecting places which have tho 
same thermic anomaly, or deviation of the ob- 
served mean temperature of a certain period 
(month, season, or year) from the normal tem- 
perature, or that which is due to a locality in 
respect of its latitude alone. Also isabnormal. 
Dore has published an elaborate set of maps construct- 
ed on this principle, In which he shows by a system of 
Thermic IgaunorituUg the deviations from the mean of each 
month, and of the year, on the different parts of tho 
globe. Ruchan, Handy-book of Meteorology, p. 126. 
isobar (i'so-biir), . [< Gr. toof, equal, + ftapo^, 
weight: see barometer.] In phys. geoq., a line 
connecting places on the surface of the globe 
at which the barometric pressure is the same. 
For places not situated at the sea-level, a correction must 
be applied to each barometric observation corresponding 
to the elevations of the stations, before the isobar connect- 
ing such stations can be drawn. Isobars may be purely 
imaginary lines ; but generally, that the distribution of 
the pressure may be seen at a glance, they are drawn 
upon some kind of map or chart of the regions covered 
by the observations, isobars may be such as indicate 
the distribution of barometric pressure at a certain speci- 
fied day and hour, or they may give the mean pressure for 
any period of time, as for the entire ><':irur f->r the suimm'r 
or winter months. Also called isftkarnmetric line. 
A study of the isobars at different seasons throws light 
upon all periodical occurrences in the way of winds and 
currents. Encyc. Brit., XVIII. 117. 
isobaric (i-so-bar'ik), a. [< isobar + -ic.] In- 
dicating equal weight or pressure, especially 
the pressure of the atmosphere : in the latter 
use equivalent to isobarometric. 
3195 
isobarism (i'so-biir-izm), M. [< ixolmr + -ixni.] 
Equality or similarity of weight. 
isobarometric (i-so-bar-o-met'rik), a. [< Gr. 
""".', equal, + E. barometric.] In phyx. geog., in- 
dicating equal barometric pressure. Also iso- 
linrii: _ iBObarometrlc line. Same as isobar. 
isobathytherm (i-so-bath'i-tWrm), . [< Gr. 
laof, equal, + jiadvf, deep, + Hlp/a/. heat.] A 
line connecting points in a vertical section of 
any part of the ocean which have the same tem- 
perature. .s'/Y ('. II'. Thomson, 1876. 
isobathythermal (J-so-bath-i-ther'mal), a. [< 
i.^iljii/liittlti-rin + -al.] Of or pertaining to an 
isobathytherm ; isobathythermic. 
isobathythermic (i-so-bath-i-ther'mik), a. [< 
isobathytherm + -ic.] Relating to an isobathy- 
thenn ; having the same degree of temperature 
at the same depth of the sea. 
isobilateral (I'so-bi-lat'e-ral). a. [< Gr. laof, 
equal, + E. bilateral.] labot., having the flanks 
of the organ flattened surfaces: applied to a 
particular kind of bilaterally symmetrical or- 
gans, as the leaves of some species of 7m, in 
contradistinction from bifacial or dorsiventral 
organs, or those with an evident upper and un- 
der surface, as in most leaves. 
isobrious (i-sob'ri-us), a. [< Gr. laoc, equal, + 
fipiav, be strong, make strong.] In hot., grow- 
ing or seeming to grow with equal vigor in both 
lobes: applied to a dicotyledonous embryo. 
Also isodynamous. 
isobront (i'so-bront), n. [< Gr. laoc, equal, + 
fipovrii, thunder.] A line on a map or chart 
connecting those places at which a given peal 
of thunder is heard simultaneously. 
The isnbronts, or the lines uniting the places where the 
first peal of thunder was simultaneously neard. 
Set. Amer. Supp., p. 9154. 
Isocardia (i-so-kar'di-il), n. [< Gr. laoc, equal, 
+ unpaid = E. heart.] A genus of heart- 
cockles, of the fam- 
ily Isocardiida:. They 
have a cordate ventricose 
shell, with separated in- 
volute divergent beaks, 
the cardinal teeth 2 and 
the laterals 1 or 2 in each 
valve. The extinct spe- 
cies are numerous, and, 
there are five living spe- 
cies. I. cor is an example. 
Glosnts is a synonym. 
Isocardiidae (i'so- 
kiir-di'i-de), n. pi. 
[NL., < Isocardia + 
-ida;.] A family of 
siphonate bivalve 
mollusks, named H ,tx*ie (/,**, n. 
from the genus Iso- 
cardia; the heart-cockles. They have the shell 
cordiform and ventricose, and the beaks sometimes sub- 
spiral, 2 cardinal and 1 or 2 lateral teeth in each valve, the 
muscular impressions narrow, and the pallial line simple. 
Isocardia cor, the heart-shell or ox-horn cockle, occurs In 
the European seas. Glossidce is a synonym. Also Isncar- 
diadte. 
Isocarpae (I-so-kar'pe), n.pl. [NL., < Gr. laoc, 
equal, + napiroc, fruit.] A division sometimes 
made of dicotyledonous gamopetalous plants, 
consisting of those in which the carpels are of 
the same number as the divisions of the calyx 
and corolla, as in tho Ericacea?, Primulacece, etc. 
Isocarpese (i-so-kar'pe-e), n. pi. [NL. (Kut- 
zing, 1843), < Gr. looc, equal, + Kapir&c,, fruit, + 
-ece.] The first of the two classes into which 
Etttzing divided all algee. It included the tribes 
Gymnospermea; and Angiospermece. 
isocellular (I-so-sel'u-iar), a. [< Gr. looc, equal, 
+ NL. cellula, cell.] Consisting of equal or 
similar cells: as, an isocellular protozoan: op- 
posed to heterocellular. 
isocephaly (I-so-sef'a-li), n. [< Gr. looc,, equal, 
-I- />E0a?.//, the 
head.] A rule 
or principle il- 
lustrated in an- 
cientGreekart, 
in accordance 
with which, for 
the sake of sym- 
metry, natural 
proportions 
were somewhat 
sacrificed in 
certain reliefs, 
etc., notably in 
friezes, and the heads of all the figures, whether 
mounted or on foot, standing or seated, were 
carved upon nearly the same level. Also iso- 
kephaly. 
Isocephaly. Example from the frieze of 
the Parthenon. 
isoclinal 
isocercal (i-so-Vkal). . [< Gr. i<rof, equal, 
+ K/Mof, tail.] Having the end of the veit. 
bral column straight, and not bent up, as a 
fish. 
The itncercal tall without a caudal fin. 
Stand. Nat. ., m. 1*1. 
isocercy (i'so-ser-si). n. [< Gr. iaof, equal, + 
KffiKof, tail.] Iniehth., the condition of having 
an isocercal tail. 
isochasm (i'so-kazm), n. [< Gr. laof, equal, + 
X''"!'", a gap/ohasm.] An isocbasmie fine. 
isochasmic (i-so-kaz'mik), a. [< isochasm + 
-ic.] Indicating equality as regards frequency 
of auroral displays isocnaamlc curves, imaginary 
lines on the earth's surface passing through points having 
the same annual number of auroras. 
It will be noticed that, eastward from England, the i- 
chaxmic curves tend rapidly northward, Archangel being 
only on the same auroral parallel as Newcastle. 
Encyc. BrlL, III. 97. 
isochela (I-so-ke'lii), n.; pi. isochelte (-le). [< 
Gr. ioof, equal, + xtfJi, claw.] In sponges, an 
anchorate or anchor-shaped flesh-spicule ; a 
curved spicule with equal ends extended on the 
surface of a rotation ellipsoid, and having both 
these ends flat and expanded. See cut under 
ancora^. 
isochimal (i'so-ki-mal), a. [< isochime + -al.] 
Of the same mean winter temperature. Also 
spelled isocheimal Igocnlmal line. Same as ito- 
chime. 
isochime (i'so-kim), . [< Gr. (<rof, equal, + 
Xti/ia, winter: see hiemal.'] In phys.geoy.,ti\ine 
drawn on the map through places on the surface 
of the globe which have the same mean winter 
temperature. Also spelled isochcim. 
isochimenal (i-so-ki'me-nal), a. Same as iso- 
chimal. 
isochimonal, isocheimonal (i-so-ki'mo-nal), 
a. [< Gr. ioof, equal, + x ei f"-> v > winter, + -al.] 
Same as isochimal. 
isochor (i'so-kdr), . [< Gr. iaof, equal, + x^f", 
space, room.] A curve of equal volume upon a 
diagram in which the rectangular coordinates 
represent pressure ami temperature. 
isochoric (i-so-kor'ik), a. [< isochor + -ic.] 
Pertaining to'equal volume or density: as, an 
isochoric curve. 
isochromatic (i"so-kro-mat'ik), a. [< Gr. laof, 
equal, + ,r/)w/ia(r-'), color: see chromatic.] 1. 
Having the same color : said of the two series of 
oval curves of the interference figures of biax- 
ial crystals. Each curve In the one series has one cor- 
responding to It both in form and color In the other. The 
two curves or lines that have the same tint are called uo- 
chrotnatic Una. See interference fiyuret, under interfer- 
ence, s. 
Beside these (dark bandsl. there are also variable bands, 
which correspond to the brushes which cross the igochro- 
matic curves. Sputtimuode, Polarisation, p. 78. 
2. In photog., game as ortliochroniatic. 
isochronal (i-sok'ro-nal). a. [As isocliron-ous 
+ -al.] Uniform in time; of equal time; per- 
formed in equal times. Two pendulums which 
vibrate in the same time are Isochronal : also, the vibra- 
tions of a pendulum in the curve of a cycloid have the 
same property, being all performed In the same time, 
whether the arc he large or small. Also tgocAronoux. 
Isochronal line, a line in which a heavy body descends 
without acceleration or retardation. 
isochronally (i-sok'ro-nal-i), adv. So as to be 
isochronal; with uniformity or equality of time. 
Also isochrottovxly. 
isochronic (i-so-krpn'ik), a. [As isochron- 
ous + -ic.] Occurring at regular intervals of 
time. 
isochronism (i-sok'ro-nizm), n. [As isochro- 
nous + -ism.] The character of being isochro- 
nous ; the property of a pendulum by which it 
performs its vibrations in equal times. 
isochronon (I-sok'ro-non), n. [< Gr. laAxpovav, 
neut. of ia6xpovof, equal in time: see isochro- 
nous.] An equal time-keeper; a clock designed 
to keep perfectly accurate time. 
isochronous (I-sok'ro-nus), a. [< Gr. loAxpovof , 
equal in ago or time. < laof, equal, + ;tpovor, 
time: see chronic.] Same us isochronal. 
isochronously (i-sok'ro-uus-li), adv. Same as 
isochronally. 
isochroous (I-sok'ro-us), a. [< Gr. iaoxpoos , like- 
colored, < (<rof, equal, T XP> color.] Being of 
the same color throughout; whole-colored. 
isoclinal (i-so-kli'nal), a. and . [As isoclitte + 
-al.] I. a. 'Of equal inclination: applied in 
geology to strata which incline or dip in the 
same direction. See monoclinal. 
The flexures are often so rapid that after denudation of 
the tops of the arches the strata are uoclinal, or appear to 
be dipping all In the same direction. 
A. Oeitie, Text Book of Geology, p. 930. 
