RADHANPUR 



6459 



RADICAL 



Radhanpur. Native state and 

 town of India, in Palanpur agency, 

 Bombay Prov. The state lies be- 

 tween Baroda and the Rann of 

 Cutch, and is drained by intermit- 

 tent streams, rising in Mt. Abu. 

 The town lies 150 m. N.W. of 

 Baroda and is a centre for minor 

 roads in an unimportant part of the 

 prov. There is some local trade 

 in wheat, grain, cotton, rice, and 

 sugar. Area 1,150 sq. m. Pop., 

 state, 65,600: town, 11,600.^ 



Radial Artery. Artery running 

 from immediately below the bend 

 of the elbow to the outer side of the 

 palm of the hand. Just before 

 crossing over the wrist it can be 

 felt beating beneath the skin, form- 

 ing there the well-known pulse. 



Radial Nerve. One of the ter- 

 minal branches of the musculo- 

 spiral nerve (q.v.). It is the nerve 

 of sensation to the back of the 

 lower third of the forearm and the 

 back of the thumb, the index and 

 middle fingers, and the outer side 

 of the ring finger. 



Radiant. In astronomy, the 

 point in the sky from which the 

 meteors or a meteor shower appear 

 to radiate. This apparent radiation 

 is an effect of perspective, the ac- 

 tual paths of the meteors being 

 nearly parallel. The majority of 

 meteor showers are named from 

 the positions of their radiant points, 

 e.g. the Perseids, which have their 

 radiant point in the constellation 

 of Perseus. See Meteor. 



Radiata. Name given by Cuvier 

 in 1812 to the lowest of his divisions 

 of the animal kingdom. It in- 

 cluded a heterogeneous multitude 

 of animals echinoderms, worms, 

 polyps, and protozoa which were 

 supposed to have their organiza- 

 tion arranged radially instead of 

 bilaterally. Huxley finally broke 

 up what he called " the radiate 

 mob," and the name is not now 

 used in zoology. 



Radiation. Name given to 

 energy, emitted by material bodies, 

 which traverses space without the 

 aid of an apparent material 

 medium. According to the electro- 

 magnetic theory such energy is 

 dependent on wave motion in the ( 

 ether. 



This theory has been modified 

 during the 20th century by the 

 ideas which have arisen from new 

 conceptions of the atom and of the 

 release of its energies by the dislo- 

 cations or the recombinations of 

 the electric ions within it ; so that, 

 according to views enunciated by 

 Planck and accepted by many 

 modern physicists, radiant energy 

 does not consist of transverse 

 waves in the ether, but of minute 

 pulses of energy, called by Planck 

 quanta. Radiant energy according 



to the doctrine would be produced 

 by an increased velocity, an acceler- 

 ation, of electric charges in the 

 atom. The theory has been ex- 

 perimentally verified in many 

 fields of science. 



Radiant energy as commonly 

 understood may be explained from 

 the example of a hot body sus- 

 pended in air, or any gas. There 

 is loss of heat due to conduction 

 through the gas or convection 

 currents set up in it, and this loss 

 of heat depends on the presence of 

 material particles in the gas. But 

 if the hot body were suspended in a 

 perfect vacuum, it would still shed 

 its heat, or radiate its energy, in all 

 directions, quite independently of 

 the absence of material particles. 



It was shown by Newton that a 

 body radiated heat in a steady 

 current of air at a rate propor- 

 tional to the difference of tempera- 

 ture of the body and the air. In 

 still air the law is more compli- 

 cated, heated bodies radiating 

 their heat according to the fourth 

 power of the temperature differ- 

 ence. The law is due to Stefan, by 

 whose name it is known, and has 

 been proved experimentally over a 

 large range of temperatures. An- 

 other law of radiating bodies is that 

 they radiate most freely those rays 

 which they absorb most freely. 

 Thus glass absorbs the infra red 

 rays, and on heating radiates them 

 to a greater extent than substances 

 which are transparent to the rays. 



The radiant heat which reaches 

 the earth from the sun passes 

 through space, which so nearly 

 approaches a vacuum as to be in- 

 distinguishable from it ; and this 

 space is presumed not to be heated 

 by the radiations of energy passing 

 through it, though the presump- 

 tion cannot be imhesitatingly 

 accepted. By the analogy of a 

 body suspended in a closed 

 vacuum vessel, the walls of which 

 are of higher or lower temperature 

 than the body, we can arrive at the 

 condition which obtains between a 

 body like the sun, which is always 

 radiating energy, and one which, 

 like the earth, is always receiving 

 .it. It is clear that the body in the 

 'Vacuum will continually radiate 

 energy. See Energy ; Heat ; Light ; 

 Radium. 



Radiator. Apparatus for radi- 

 ating or dissipating heat. A motor- 

 car radiator consists of a number of 

 metal tubes, through which water 

 used for cooling the engine circu- 

 lates. The tubes are externally 

 connected by thin webs, or are sur- 

 rounded by a great number of thin 

 disks, preferably of copper or other 

 good, heat-conducting metal. The 

 radiator is so placed on a car 

 that when the latter is in motion 



pressure causes the air to pass 

 through the spaces between the 

 webs or disks and dissipate the 

 heat ; at a speed of 20 m. an hour 

 or more through still air the pres- 

 sure is sufficient for this purpose, 

 but to ensure a constant stream of 

 air at lower speeds, or when the 

 car is stationary and the engine 

 running, a fan is fitted at the rear 

 of the radiator and revolved at high 

 speed by a belt and pulley driven 

 from the engine shaft. 



Radiators for heating rooms 

 and buildings consist of frames of 

 tubes, designed to present the 

 greatest possible superficial area 

 to the ah 1 , coupled up to piping 

 through which hot water, steam, or 

 hot air is circulated. They are 

 placed on the ground so that, as 

 the air surrounding them is heated, 

 it rises, cooler air takes its place, 

 and a circulation of air is main- 

 tained. In electric radiators heat 

 is generated by passing an electric 

 current through resistance coils, 

 which in some cases are enclosed in 

 glass bulbs and give light as well 

 as heat. See Heating ; Motor Car. 



Radical OR RADICLE (Lat. radix, 

 root). Term applied in chemistry 

 to elements (simple radicals) or 

 groups of elements (compound 

 radicals). It usually denotes a 

 compound radical or group of 

 units capable of passing unaltered 

 from compound to compound. 

 The names of radicals generally 

 end in the syllable -yl, examples 

 being hydroxyl (OH) ; carbonyl 

 (CO) ; thionyl (SO) ; methyl (CH 3 ) ; 

 carboxyl (COOH); sulphuryl (S0 2 ); 

 phosphoryl (PO); nitroxyl (N0 2 ). 

 Exceptions to this rule are ammo- 

 nium (NH 4 ) and cyanogen (CN). 

 Radicals are either of a positive, 

 basic, or metallic nature, or negative 

 or acidic, and do not mix in a free 

 state. 



Radical (Lat. radix, root). 

 Term applied to those who desire 

 large changes in the social and 

 political order. In Great Britain 

 the radical party has been an ad- 

 vanced section of the Liberal 

 party ; its equivalent in France is 

 the left. The word was first used 

 for politicians towards 1800, and 

 after the French Revolution it 

 became a popular term for those 

 Orator Hunt being among them 

 who held advanced opinions. It 

 was also applied to thinkers such as 

 Bentham and James Mill, who 

 tried to introduce a philosophic 

 theory of government based on 

 first principles. They were indi- 

 vidualists and economists, but 

 later radicals bel eved in a constant 

 enlargement of the area of state 

 control. See I/jft; Liberal; Poli- 

 tics ; consult also The English 

 Radical, C. B. R. Kent, 1899. 



