radiation 
chiefly upon the temperature of the body ; it is called lu- 
minous or obscure, according as it Is or is not capable; uf 
exciting the sensation of light. See further radiant energy 
(under eneryy), alsu heat, linhti, ttpectrum. 
Radiation is the rommniiirjition of vibratory motion to 
the ether, and when a body is said to be chilled by radia- 
tion, as for example the grass of a meadow on a starlight 
night, the meaning is that the molecules of the grass have 
lost a portion of their motion, by imparting it to the 
medium in which they vibrate. Tyiutall, Radiation, 2. 
Any substance . . . will become heated by radiation to 
the greatest degree when its surface is made rough anil 
completely black, so that it can absorb all the rays falling 
upon it. Lmmml, Light (trans.), p. 198. 
2. The divergence or shooting forth of rays 
from a point or focus. 3. In zool., the struc- 
tural character of a radiate ; the radiate con- 
dition, quality, or type; the radiate arrange- 
ment of parts. Also radiimii Direct radiation 
and indirect radiation, phrases used in describing the 
method of heating by steam-radiators, according as the 
radiator is actually in the room heated or is inclosed in a 
space beneath, from which the hot air is distributed by 
tin pipes, as in simple heating by a hot-air furnace. In 
both cases the heat is communicated by convection, and 
in the case of indirect radiation not at all by radiation. 
Dynamic radiation, a phrase introduced by Tyndall 
to describe the radiation of a pas when the heat is not 
due to an outside source, but is developed by the molecu- 
lar motion as the gas passes rapidly into an exhausted 
vessel. Solar radiation, the radiation of the sun as 
measured by the heat which the earth receives from it. 
Terrestrial radiation, the communication of heat 
by the earth to the surrounding ether, by means of radia- 
tion. 
radiative (ra'di-a-tiv), . [< radiate + -4ve.~\ 
Having a tendency to radiate ; possessing the 
quality of radiation. Radiative or radiating 
power, the ability of a body to radiate heat that is, phys- 
ically, to transform its own heat-energy into the wave- 
motion of the surrounding ether. It depends, other 
things being equal, upon the nature of the surface of the 
body, being a maximum for lampblack and a minimum 
for polished metallic surfaces : thus, a mass of hot water 
will cool more rapidly in a vessel with a dull-black sur- 
face than in one which is polished and bright, like silver. 
The radiative and absorbing powers of a substance are 
identical, and are the opposite of the reflecting power. 
Also called emissive power. 
radiator (ra'di-a-tor), i. [< radiate + -or 1 .] 1. 
Anything which radiates ; a body or substance 
from which rays of heat emanate or radiate. 
2. A part of a heating apparatus designed to 
communicate heat to a room, chiefly by con- 
vection, but partly, in some cases, by radiation. 
upward through passages in base k'. c, an indirect steam -radiator: .... 
base ; f, tubes ; cold air from without is admitted at /, and passes over 
radiator as indicated by arrows; k, flues up which warm air passes 
to register./. 
A common form of radiator is a sheet-iron drum or cyl- 
inder containing deflectors or baffle-plates, placed over a 
fireplace to cause the volatile products of combustion to 
give up their heat as they pass: a heating-drum. A steam- 
radiator consists of a mass of coiled or flexed pipes to which 
steam for heating is conveyed through a continuous pipe 
from a boiler, and which is provided with suitable valves 
for the control of the steam. 
radiatory (ra'di-a-to-ri), . [< radiate 4- -or#.] 
Radiating; having parts arranged like rays 
around a center or axis; rayed; actinomeric. 
radical (rad'i-kal), a. and n. [< F. radical = 
Pr. Sp. Pg. radical = It. radicale = D. radikaal 
= Gr. Sw. Dan. radikal, < LL. radical-is, of or 
pertaining to the root, having roots, radical, 
< L. radix (radio-), root: see radix."] I. a. 1. 
Pertaining or relating to a root or to roots. 
The cause of a thynne and watery radycall moyster to 
suche thynges as drawe theyr nuryshement therof. 
.R. Eden, tr. of Gonzalus Oviedus (First Books on America, 
[ed. Arber, p. 227). 
Specifically (a) In bat., belonging to the root: opposed 
to cauline. See radical leaven and radical pedurtcle, be- 
low. (6) In phUnl., of the nature of or pertaining to a 
root, or a primary or underived word or main part of a 
word : as, a radical word ; a radical letter or syllable ; 
radical accentuation, (c) In math., consisting of or in- 
dicating one <>f tlit- nmts of a number: as, a radical ex- 
pression ; tin- rit'ii'rtil H;JU. (il) In cheat., noting any atom 
4933 
or group of atoms which is, for the moment, regarded as a 
chief constituent of the molecules uf a given compound, 
and which does not lose its integrity in the ordinary i-hein- 
ical reactions to which the substance is liable. Coofce, 
(.'hem. Philos., p. 106. 
2. Making part of the essential nature of the 
subject or thing concerned ; existing inherent- 
ly; intrinsic; organic: as, radical defects of 
character; a radical fault of construction ; tin- 
radical principles of an art or of religion. The 
Latin word first occurs, about the beginning of the tbii - 
teenth century, in the phrase humidum radicale, or radi- 
cal moisture, that moisture in an animal or a plant which 
cannot be expelled without killing the organism which 
was supposed to remain unchanged throughout life, and 
to be the chief principle of vitality. The word seeuis to 
translate the pseudo-Aristotelian u>s dp eiwot TIS piai, 'as 
one may say, roots' an expression applied to moisture 
and certain other conditions as being essential to the life 
of plants. 
Radicall moisture, or first or naturall moisture, spml 
like a dew thorow all the parts of the bodie, wherewith 
such parts are nourished : which moisture, being once 
wasted, can neuer be restored. Minsheit. 
Whilst thus my sorrow-wasting soul was feeding 
Upon the radical humour of her thought. 
Quarles, Emblems, iv. 12. 
This radical error . . . has contributed more than any 
other cause to prevent the formation of popular constitu- 
tional governments. Calhoun, Works, I. 30. 
3. Of or pertaining to the root or foundation 
of the subject ; concerned with or based upon 
fundamental principles; hence, thoroughgoing; 
extreme: as, a radical truth; a radical differ- 
ence of opinion; radical views ,or measures; the 
Radical party in British politics. 
His works ... are more radical in spirit and tendency 
than any others, for they strike at all cant whatever, 
whether it be the cant of monarchy or the cant of democ- 
racy. Whipple, Ess. and Rev., I. 147. 
4. {cap.'] Of or pertaining to a political party 
or body of persons known as Radicals (see 
II., 4, below): as, a Radical candidate; the 
Radical program Radi- 
cal axis of two circles. 
See aaasi. Radical bass, in 
music, same as fundamental 
bass (which see, under /unda- 
mental). Radical cadence, 
in immc, a cadence consisting 
of chords in their original posi- 
tion. Radical center of 
three circles in a plane, the 
intersection of the three radi- 
cal axes of the three pairs of the 
three circles. Radical curve. See curve. Radical 
expression, an expression containing radical signs, es- 
pecially a quantity expressed as a root of another. Some- 
times loosely called a radical quantity. Radical func- 
tion. See function. Radical leaves, leaves springing 
from the root, or, properly, from a part of the stem near to 
and resembling the root. In many herbs (primrose, dan- 
delion, etc.) all or nearly all the leaves are thus clustered 
at the base of the stem. See cuts under Hieracium and 
Ornithoyalum. Radical molsturet. See above, def. 2. 
Radical peduncle, a peduncle that proceeds from the 
axil of a radical leaf, as in the primrose and cowslip. 
Radical pitch, the pitch or tone with which the utter- 
ance of a syllable begins. Radical plane, the plane of 
intersection of two spheres other than the plane at in- 
finity, whether the circle of intersection be real or not. 
Radical Sign, the sign y (a modified form of the letter 
r, the initial of Latin radix, root), placed before any quan- 
tity, denoting that its root is to be extracted : thus, \ a or 
y a + b. To distinguish the particular root, a number is 
written over the sign : thus, f , ^ , y , etc., denote 
respectively the square root, cube root, fourth root, etc. 
In the case of the square root, however, the number is 
usually omitted, and merely the sign written. The same 
sign is much used to mark a so-called root or radical ele- 
ment of words. Radical Stress, in elocution, the force 
of utterance falling on the initial part of a syllable or word. 
= Syn. 3. There may be a distinction between a radical 
reform, change, cure, or the like, and one that is thorough, 
entire, complete, or thoroughgoing, radical emphasizing only 
the fact of going to the root, whether there is thorough- 
ness or entireness or not. Yet that which is radical is 
likely to be thorough, etc. 
II. n. 1. In philol.: (a) A radical word or 
part of a word; especially, a primitive word 
or verbal element serving as a root of inflected 
or derivative words. (6) A radical letter; a 
letter forming an essential part of the primitive 
form or root of a word. Also radicle. 2. In 
ehem., an element or group of combined ele- 
ments which remains after one or more ele- 
ments have been removed from a compound. 
(See the quotation.) The term is chiefly applied to 
compound radicals, which are assumed to exist in com- 
pound bodies and to remain intact in many of the chem- 
ical changes which these bodies undergo. Thus the com- 
pound radical ethyl, CoHs, appears in alcohol (CoHs-OHX 
in ether ((C 2 H 5 )20X in ethylamine(C 2 H 5 .NH 2 ) ) etc., and 
may be transferred without change, like an element, from 
one of these compounds to the other. Also radicle. 
The word radical stands for any atom or group of atoms 
which is, for the moment, regarded as a chief constituent 
of the molecules of a given compound, and which does 
not lose its integrity in the ordinary chemical reactions 
to which the substance is liable. ... As a general rule 
the metallic atoms are basic radicals, while the non-metal- 
lic atoms are acid radicals. . . . Among compound radical* 
Radical Axes and Radical 
Center. 
radicant 
those consisting of carbon and hydrogen alone are usu- 
ally basic, and those containing oxygen also are usually 
acid. Coolce, Chem. Philos., p. 108. 
3. In iiiuxir, same as root. 4. A person who 
holds or acts according to radical principles ; 
one who pursues a theory to its furthest appar- 
ent limit ; an extremist, especially in politics. 
In the political sense, in which the word has been most 
used, a Radical is one who aims at thorough reform in 
government from a liberal or democratic point of view, 
or desires the establishment of what he regards as abstract 
principles of right and justice, by the most direct and 
uncompromising methods. The political Radicals of a 
country generally constitute the extreme faction or wing 
of the more liberal of the two leading parties, or act as a 
separate party when their numbers are sufficient for the 
exertion of any considerable influence. The name Radi- 
cal is often applied as one of reproach to the members of 
a party by their opponents. In the United States it has 
been so applied at times to Democrats, and to Republi- 
cans especially in the South about the period of recon- 
struction. The French Radicals are often called the 
Extreme Left. The British Radicals form an important 
section of the Liberal party. 
In politics they [the Independents] were, to use the 
phrase of then- own time, "Hoot-and-Bianch men," or, to 
use the kindred phrase of our own, Radicals. Macaulay. 
He [President Johnson] did not receive a single South- 
ern vote, and was detested through every Southern State 
with a cordiality unknown in the case of any Northern 
Iladical. The Nation, III. 141. 
5. In aly., a quantity expressed as a root of 
another quantity Negative, organic, etc., radi- 
cal. See the adjectives. 
radicalise, v. See radicalize. 
radicalism (rad'i-kal-izm), n. [= F. radica- 
lisme = Sp. Pg. It. " radicalismo ; as radical + 
-ism.'] The state or character of being radical; 
the holding or carrying put of extreme princi- 
ples on any subject ; specifically, extreme politi- 
cal liberalism ; the doctrine or principle of un- 
compromising reform in government; the sys- 
tem or methods advocated by the political Radi- 
cals of a country. 
Radicalism endeavours to realize a state more in har- 
mony with the character of the ideal man. 
H. Spencer, Social Statics, p. 511. 
The year 1769 is veiy memorable in political history, for 
it witnessed the birth of English Radicalism, and the nrst 
serious attempts to reform and control Parliament by a 
pressure from without, making its members habitually 
subservient to their constituents. 
Lecty, Eng. in 18th Cent., xi. 
radicality (rad-i-kal'i-ti), . [< radical + -%.] 
1. The state or character of being radical, in 
any sense. [Rare.] 2f. Origination. 
There may be equivocal seeds and hemiaphroditical 
principles which contain the radicality and power of 
different forms. Sir T. Browne, Vulg. Err., iii. 17. 
radicalize (rad'i-kal-Jz), v. ; pret. and pp. radi- 
calized, ppr. radicalizing. [< radical + -ize.~\ 
1. trans. To make radical; cause to conform 
to radical ideas, or to political radicalism. 
[Recent.] 
It is inferred . . . that Lord Salisbury means to radical- 
ize his land programme for England. 
Sea York Tribune, Feb. 18, 1887. 
II. infra us. To become radical ; adopt or 
carry out radical principles, or the doctrines of 
political radicalism. [Recent.] 
Indeed, it is hard to say which is the more surprising 
the goodwill shown by the Russians, and even by the 
Russian Government, for a radicalising Republic, or the 
fatuous admiration of certain French Republicans for the 
most autocratic State in Europe. 
Contemporary Rev., L1II. 303. 
Also spelled radicalise. 
radically (rad'i-kal-i), adv. 1. By root or 
origin ; primitively ; originally ; naturally. 
Tho' the Word [bless] be radically derived from the 
Dutch Word, yet it would bear good Sense, and be very 
pertinent to this Purpose, if we would fetch it from the 
French Word " blesser," which is to hurt. 
Hawell, Letters, I. vi. 55. 
These great Orbs thus radically bright. 
Prior, Solomon, i. 
2. In a radical manner ; at the origin or root ; 
fundamentally ; essentially : as, a scheme or 
system radically wrong or defective. 
The window tax, long condemned by universal consent 
as a radically bad tax. 
8. Dowell, Taxes in England, II. 313. 
radicalness (rad'i-kal-nes), . The state of be- 
ing radical, in any sense. 
radicand (rad-i-kand'), . [< L. radicandus, 
ger. of radicari, take root: see radicate.'] In 
math., an expression of which a root is to be 
extracted. 
radicant (rad'i-kant), a. [< F. radicant, < L. 
radican(t-)s, ppr. of radicari, take root: see 
radicate.'] In bot., rooting; specifically, pro- 
ducing roots from some part other than the 
descending axis, as for the purpose of climb- 
ing. Also radicating. 
