WILHELM EDUARD See also:

• WEBER, CARL MARIA FRIEDRICH ERNEST VON (1786–1826)
• WILHELM EDUARD WEBER (1804-1891)

WEBER (1804-1891)  , See also:

• GERMAN
• GERMAN, DUTCH AND SCANDINAVIAN

German physicist, was See also:

• BORN, IGNAZ, EDLER VON (1742–1791)

born at See also:

• WITTENBERG

Wittenberg on the 24th of See also:

• OCTOBER

October 1804, and was a younger See also:

• BROTHER

brother of See also:

• ERNST, HEINRICH WILHELM (1814–1865)

Ernst Heinrich See also:

• WEBER, CARL MARIA FRIEDRICH ERNEST VON (1786–1826)
• WEBER, WILHELM EDUARD (1804-1891)

Weber, the author of Weber's See also:

• LAW
• LAW (0. Eng. lagu, M. Eng. lawe; from an old Teutonic root lag, " lie," what lies fixed or evenly; cf. Lat. lex, Fr. loi)
• LAW, JOHN (1671—1729)
• LAW, WILLIAM (1686-1761)

Law (see below) . He studied at the university of See also:

• HALLE (known as HALLE-AN-DER-SAALE, t0 distinguish it from the small town of Halle in Westphalia)
• HALLE, SIR CHARLES (originally KARL HALLE) (1819-1895)

Halle, where he took his See also:

• DOCTOR (Lat. for " teacher ")

doctor's degree in 1826 and became extraordinary See also:

• PROFESSOR (the Latin noun formed from the verb profiteri, to declare publicly, to acknowledge, profess)

professor of physics in 1828 . Three years later he removed to See also:

• GOTTINGEN

Gottingen as professor of physics, and remained there till 1839, when he was one of the seven professors who were expelled from their chairs for protesting against the See also:

• ACTION

action of the See also:

• KING
• KING (O. Eng. cyning, abbreviated into cyng, cing; cf. O. H. G. chun- kuning, chun- kunig, M.H.G. kiinic, kiinec, kiinc, Mod. Ger. Konig, O. Norse konungr, kongr, Swed. konung, kung)
• KING [OF OCKHAM], PETER KING, 1ST BARON (1669-1734)
• KING, CHARLES WILLIAM (1818-1888)
• KING, CLARENCE (1842–1901)
• KING, EDWARD (1612–1637)
• KING, EDWARD (1829–1910)
• KING, HENRY (1591-1669)
• KING, RUFUS (1755–1827)
• KING, THOMAS (1730–1805)
• KING, WILLIAM (1650-1729)
• KING, WILLIAM (1663–1712)

king of See also:

• HANOVER
• HANOVER (Ger. Hannover)

Hanover (See also:

• DUKE (corresponding to Fr. duc, Ital. duca, Ger. Herzog)

duke of See also:

• CUMBERLAND
• CUMBERLAND, DUKES AND EARLS OF
• CUMBERLAND, RICHARD (1632-1718)
• CUMBERLAND, RICHARD (1732-1811)
• CUMBERLAND, WILLIAM AUGUSTUS

Cumberland) in suspending the constitution . A See also:

• PERIOD
• PERIOD (Gr. irepioSos, a going or way round, circuit, aepi, round, and &Sis, way, road)

period of retirement followed this See also:

• EPISODE

episode, but in 1843 he accepted the See also:

• CHAIR (in. Mid. Eng. chcere, through O. Fr. chaire or chaiere, from Lat. cathedra, later caledra, Gr. xaOi3pa, seat, cf. "cathedral"; the modern Fr. form chaise, a chair, has been adopted in English with a particular meaning as a form of carriage; chaire

chair of physics at See also:

• LEIPZIG

Leipzig, and six years later returned to Gottingen, where he died on the 23rd of See also:

• JUNE

June 1891 . Weber's name is especially known for his See also:

• WORK

work on See also:

• ELECTRICAL
• ELECTRICAL (or ELECTROSTATIC) MACHINE

electrical measurement . Until his See also:

• TIME (0. Eng. Lima, cf. Icel. timi, Swed. timme, hour, Dan. time; from the root also seen in " tide," properly the time of between the flow and ebb of the sea, cf. O. Eng. getidan, to happen, " even-tide," &c.; it is not directly related to Lat. tempus)
• TIME, MEASUREMENT OF
• TIME, STANDARD

time there was no established See also:

• SYSTEM

system either of stating or measuring electrical quantities; but he showed, as his colleague K . F . See also:

• GAUSS, KARL FRIEDRICH (1777-1855)

Gauss did for magnetic quantities, that it is both theoretically and practically possible to define them, not merely by reference to other arbitrary quantities of the same See also:

• KIND (O. E. ge-cynde, from the same root as is seen in " kin," supra)

kind, but absolutely in terms in which the See also:

• UNITS, DIMENSIONS OF
• UNITS, PHYSICAL

units of length, time, and See also:

• MASS (O.E. maesse; Fr. messe; Ger. Messe; Ital. messa; from eccl. Lat. missa)
• MASS, IN

mass are alone involved . He also carried on extensive researches in the theory of See also:

• MAGNETISM
• MAGNETISM, TERRESTRIAL

magnetism; and it is interesting that in connexion with his observations in terrestrial magnetism he not only employed an See also:

• EARLY
• EARLY, JUBAL ANDERSON (1816-1894)

early See also:

• FORM (Lat. forma)

form of See also:

• MIRROR (through O. Fr. mirour, mod. miroir, from a sup-posed Late Lat. miratorium, from mirari, to admire)

mirror See also:

• GALVANOMETER

galvanometer, but WEBER'S LAW also, about 1833, devised a system of electromagnetic telegraphy, by which a distance of some 9000 ft. was worked over . In See also:

• CONJUNCTION (from Lat. conjungere, to join together)

conjunction with his See also:

• ELDER (0. Eng. ellarn; Ger. Holunder; Fr. sureau)
• ELDER (Gr. 1rpev(3iTepos)

elder brother he published in 1825 a well-known See also:

• TREATISE

treatise on waves, See also:

• DIE
• DIE (Fr. de, from Lat. datum, given)

Die Wellenlehre auf Experimente gegrundet; and in 1833 he collaborated with his younger brother, the physiologist Eduard See also:

• FRIEDRICH, JOHANN (1836— )

Friedrich Weber (1806-1891), in an investigation into the mechanism of walking . WEBER'S LAW, in See also:

• PSYCHOLOGY
• PSYCHOLOGY (>Guxrl, the mind or soul, and X yos, theory)

psychology, the name given to a principle first enunciated by the German scientist, Ernst Heinrich Weber (1995-1878), who became professor at Leipzig (of See also:

• ANATOMY
• ANATOMY (Gr. avaroyil, from ava-silo c', to cut up)

anatomy, 1818, of See also:

• PHYSIOLOGY (from Gr. 4 i s, nature, and koyos, discourse)

physiology, 1840) . He was specially famous for his researches into aural and cutaneous sensations .

His law, the purport of which is that the increase of stimulus necessary to produce an increase of sensation in any sense is not a fixed quantity but depends on the proportion which the increase bears to the immediately preceding stimulus, is the See also:

• PRINCIPAL

principal generalization of that See also:

• BRANCH (from the Fr. branche, late Lat. branca, an animal's paw)

branch of scientific investigation which has come to be known as psycho-physics (q.v.) . According to Gustav See also:

• FECHNER, GUSTAV THEODOR (1801-1887)

Fechner (q.v.), who has done most to prosecute these inquiries and to consolidate them under a See also:

• SEPARATE

separate name, " psycho-physics is an exact See also:

• DOCTRINE

doctrine of the relation of See also:

• FUNCTION

function or dependence between See also:

• BODY

body and soul." In other words, it is through-out an See also:

• ATTEMPT (Lat. adtemptare, attentare, to try)

attempt to submit to definite measurement the relation of See also:

• PHYSICAL

physical stimuli to the resulting psychical or See also:

• MENTAL

mental facts, and forms an important See also:

• DEPARTMENT (Fr. departement, from departir, to separate into parts)

department of experimental psychology . It deals with the quantitative aspects of mental facts—their intensity or quantity proper and their duration . Physical See also:

• SCIENCE (Lat. scientia, from scire; to learn, know)

science enables us, at least in the See also:

• CASE
• CASE, JOHN (d. 1600)

case of some of the senses, to measure with accuracy the See also:

• OBJECTIVE, or OBJECT GLASS

objective amount of the stimulus, and See also:

• INTROSPECTION (from Lat. introspicere, to look within)

introspection enables us to See also:

• STATE
• STATE, GREAT OFFICERS OF

state the nature of the subjective result . Thus we are able to say whether a stimulus produces any psychical result, and can See also:

• FIX, THEODORE (180o-1846)

fix in that way the minimum sensibile or " See also:

• THRESHOLD

threshold of consciousness " for each of the senses . In like manner (though with less accuracy, owing to the disturbing nature of the conditions) we can fix the sensational maxi-mum, or upper limit of sensibility, in the different senses, that is to say, the point beyond which no increase of stimulus produces any appreciable increase of sensation . We thus determine, as See also:

• WUNDT, WILHELM MAX (1832— )

Wundt puts it, the limit-values between which changes of intensity in the stimulus are accompanied by changes in sensation . But the central inquiry of psycho-physics remains behind . Between the quantitative mini-mum and the quantitative maximum thus fixed can we discover any definite relation between changes in the objective intensity of the stimuli and changes in the intensity of the sensations as estimated by consciousness . The See also:

• ANSWER (derived from and, against, and the same root as swear)

answer of psycho-physics to this inquiry is given in the generalization variously known as " Weber's law," Fechner's law," or the " psycho-physical law," which professes to formulate with exactitude the relations which exist between See also:

• CHANGE (derived through the Fr. from the Late Lat. cambium, cambiare, to barter; the ultimate derivation is probably from the root which appears in the Gr. «a urmu', to bend)

change of stimulus and change of sensation . As we have no means of subjectively measuring the See also:

• ABSOLUTE (Lat. absolvere, to loose, set free)

absolute intensity of our sensations, it is necessary to depend upon the mental estimate or comparison of two or more sensations . Comparison enables us to say whether they are equal in intensity, or if unequal which is the greater and which is the less .

But as they approach equality in this respect it becomes more and more difficult to detect the difference . By a See also:

• SERIES (a Latin word from serere, to join)

series of experiments, therefore, it will be possible, in the case of any particular individual, to determine the least observable difference in intensity between two sensations of any particular sense . This least observable difference is called by Fechner the Unterschiedsschwelle or " difference-threshold," that is to say, the limit of the discriminative sensibility of the sense in question . That such a "threshold," or least observable difference, exists is See also:

• PLAIN (O. Fr. plain, from Lat. plenum)

plain from very See also:

• SIMPLE

simple examples . Very small increases may be made in the objective amount of See also:

• LIGHT

light, See also:

• SOUND
• SOUND, THE (Danish Oresund)

sound or pressure—that is, in the physical stimuli applied to these senses—without the subject on whom the experiment is made detecting any change . It is further evident that, by means of this Unterschiedsschwelle, it is possible to compare the discriminative sensibility of different individuals, or of different senses, or (as in the case of the skin) of different parts of the same sense See also:

• ORGAN

organ : the smaller the difference observable the finer the discriminative sensibility . Thus the discrimination of the See also:

• MUSCULAR

muscular sense is much more delicate than that of the sense of See also:

• TOUCH (derived through Fr. toucher from a common Teutonic and Indo-Germanic root, cf. " tug," " tuck," O. H. Ger. zucchen, to twitch or draw)

touch or pressure, and the discriminative sensibility of the skin and the retina varies very much according to the parts of the See also:

• SURFACE

surface affected . Various methods have been adopted with a view to determine these minima of discriminative sensibility with an approach to scientific precision . The first is that employed by Weber himself, and has been named the method of just observable See also:

• DIFFERENCES, CALCULUS OF (Theory of Finite Differences)

differences . It consists either in gradually adding to a given stimulus small amounts which at first cause no perceptible difference in sensation but at a certain point do cause a difference to emerge in consciousness, or, See also:

• VICE

vice versa, in gradually decreasing the amount of additional stimulus, till the difference originally perceived becomes imperceptible . By taking the See also:

• AVERAGE

average of a number of such results, the minimum may be determined with tolerable accuracy . The second method is called by Fechner the method of correct and incorrect instances .

When two stimuli are very nearly equal the subject will often fail to recognize which is the greater, saying sometimes that A is greater, sometimes that B is greater . When in a large number of trials the right and wrong guesses exactly See also:

• BALANCE (derived through the Fr. from the Late Lat. bilantia, an apparatus for weighing, from bi, two, and lanx, a dish or scale)

balance one another we may conclude that the difference between the two stimuli is not appreciable by the sense . On the other See also:

• HAND
• HAND (a word common to Teutonic languages; cf. Ger. Hand, Goth. handus)
• HAND, FERDINAND GOTTHELF (1786-185r)

hand, as soon as the number of correct guesses definitely exceeds See also:

• HALF

half of the See also:

• TOTAL

total number of cases, it may be inferred that there is a certain subjective appreciation of difference . This method was first employed by Vierordt . The third method, that of average errors, is very similar to the one just explained . Here a certain See also:

• WEIGHT

weight (to take a See also:

• CONCRETE
• CONCRETE (Lat. concretes, participle of concrescere, to grow together)

concrete example) is laid upon the hand of the See also:

• PERSON, OFFENCES AGAINST THE

person experimented upon, and he is asked, by the aid of sub- jective impression alone, to fix upon a second weight: exactly equal to the first . It is found that the second weight sometimes slightly exceeds the first, sometimes slightly falls below it . Whether above or below is of no consequence to the method, which depends solely on the amount of the See also:

• ERROR (Lat. error, from errare, to wander, to err)

error . After a number of experiments, the different errors are added together, and the result being divided by the number of experiments gives us the average error which the subject may be calculated upon to make . This marks the amount of stimulus which is just below the difference-threshold for him . This method was first employed by Fechner and Volkmann . The different methods were first named, and the theory of their application See also:

• DEVELOPED

developed by Fechner in his Elemente der Psychophysik (186o) .

A number of experimental See also:

• VARIATIONS
• VARIATIONS, CALCULUS
• VARIATIONS, CALCULUS OF

variations have since been devised by Wundt and others, but they are all reducible to the two types of the " gradation " and " error " methods . These methods have been chiefly applied to determine the relation of the difference-threshold to the absolute magnitude of the stimuli employed . For a very little reflection tells us that the smallest perceivable difference is not an amount whose absolute intensity is See also:

• CONSTANT, BENJAMIN (1845-1902)

constant even within the same sense . It varies with the intensity of the stimuli employed . We are unable, for example, to recognize slight differences in weight when the weights compared are heavy, though we should be perfectly able to make the distinction if the weights compared were both light . See also:

• ORDINARY (med. Lat. ordinarius, Fr. ordinaire)

Ordinary observation would See also:

• LEAD
• LEAD (pronounced iced)

lead us, therefore, to the conclusion that the greater the intensity of the See also:

• ORIGINAL

original stimulus at work the greater must be the increase of stimulus in See also:

• ORDER
• ORDER (through Fr. ordre, for earlier ordene, from Lat. ordo, ordinis, rank, service, arrangement; the ultimate source is generally taken to be the root seen in Lat. oriri, rise, arise, begin; cf. " origin ")
• ORDER, HOLY

order that there may be a perceptible difference in the resulting sensation . Weber was the first (after a prolonged series of experiments) to clothe this generality with scientific precision by formulating the law which has since gone by his name . He showed that the smallest perceptible difference is not absolutely the same, but remains relatively the same, that is, it remains the same fraction of the preceding stimulus . For example, if we can distinguish 16 oz. and 17 oz., we shall be able to distinguish 32 oz. and 34 oz., but not 32 oz. and 33 oz., the addition being in each case of the preceding stimulus . This fraction (supposing it to be the difference-threshold of the muscular sense) remains a constant, however light or however heavy the weights compared . The law may be formulated thus:—The difference between any two stimuli is experienced as of equal magnitude, in case the mathematical relation of these stimuli remains unaltered . Or, otherwise expressed, in order that the intensity of a sensation may increase in arithmetical progression the stimulus must increase in geometrical progression .

It is also expressed by Fechner in the form—The sensation increases as the See also:

• LOGARITHM (from Gr. Abyos, word, ratio, and apx0µos, number)

logarithm of the stimulus . The law has been variously interpreted . Fechner himself designated it the psycho-physical law, and treated it as the fundamental See also:

• FORMULA
• FORMULA (Lat. diminutive of forma, shape, pattern, &c., especially used of rules of judicial procedure)

formula of the relation between body and mind, thus assigning to it an ontological dignity and significance . But in this " psycho-physical " See also:

• INTERPRETATION (from Lat. interpretari, to expound, explain, inter pres, an agent, go-between, interpreter; inter, between, and the root pret-, possibly connected with that seen either in Greek 4 p4'ew, to speak, or irpa-rrecv, to do)

interpretation of his results he has not had a numerous following . Wundt interprets the law in a purely " psychological " sense, making it a See also:

• SPECIAL

special instance of the See also:

• GENERAL
• GENERAL (Lat. generalis, of or relating to a genus, kind or class)

general law of relativity which governs our mental states . Introspection can give us no See also:

• INFORMATION (from Lat. informare, to give shape or form to, to represent, describe)

information as to the absolute intensity of the stimulus; for a stimulus is known in consciousness only through its sensational resultant . Hence, he argues, we can only compare one psychical state with another, and our See also:

• STANDARD
• STANDARD, BATTLE OF THE

standard of measurement is therefore necessarily a relative one; it depends directly upon the preceding state with which we compare the See also:

• PRESENT

present . Others (e.g . G . E . See also:

• MULLER, FERDINAND VON, BARON (1825–1896)
• MULLER, FRIEDRICH (1749-1825)
• MULLER, GEORGE (1805-1898)
• MULLER, JOHANNES PETER (18o1-1858)
• MULLER, JOHANNES VON (1752-1809)
• MULLER, JULIUS (18oi-1878)
• MULLER, KARL OTFRIED (1797-1840)
• MULLER, LUCIAN (1836-1898)
• MULLER, WILHELM (1794-1827)
• MULLER, WILLIAM JAMES (1812-1845)

Muller) have attempted to give the law a purely physical or " physiological " explanation . Instead of holding with Fechner that the law expresses a recondite relation between the material and the spiritual See also:

• WORLD

world, they prefer to regard the quantitative relation between the last physical antecedent in the See also:

• BRAIN (A.S. braegen)

brain and the resultant mental change as prima facie one of simple proportion, and to treat Weber's law as holding between the initial physical stimulus and the final action of the See also:

• NERVE (Lat. nervus, Gr. vevpov, a bowstring)

nerve-centres .

According to this interpretation, the law would be altogether due to the nature of See also:

• NERVOUS

nervous action . As a nerve, says See also:

• SULLY, JAMES (1842– )
• SULLY, MAXIMILIEN DE BETHUNE
• SULLY, THOMAS (1783—1872)

Sully, after a temporary degree of stimulation temporarily loses its sensibility, so the greater the previous stimulation of a nerve the greater is the additional stimulus required to produce an appreciable amount of sensation . Weber's law, it must be added, holds only within certain limits . In the " chemical " senses of See also:

• TASTE (from Lat. taxare, to touch sharply; tangere, to touch)

taste and See also:

• SMELL (connected etymologically with " smoulder " and " smoke ")

smell experiments are almost impossible . It is not practicable to limit the amount of the stimulus with the necessary exactitude, and the results are further vitiated by the See also:

• LONG, GEORGE (1800-1879)
• LONG, JOHN DAVIS (1838– )

long continuance of the physiological effects . The same considerations apply with still more force to the organic sensations, andthe results in the case of temperature sensations are completely uncertain . The law is approximately true in the case of sight, See also:

• HEARING (formed from the verb " to hear," O. Eng. hyran, heron, &c., a common Teutonic verb; cf. Ger. Koren, Dutch hooren, &c.; the O. Tent. form is seen in Goth. hausjan; the initial h makes any connexion with " ear," Lat. audire, or Gr. &Kobew very doub

hearing pressure, and the muscular sense—most exactly in the case of sound . As this is the sense which affords the greatest facilities for measuring the precise amount of the stimulus, it may perhaps be inferred that, if we could attain the same exactitude in the other senses, with the elimination of the numerous disturbing extraneous influences at work, the law would vindicate itself with the same exactitude and certainty . It is further to be noted, however, that even in those senses in which it has been approximately verified, the law holds with stringency only within certain limits . The results are most exact in the See also:

• MIDDLE

middle regions of the sensory See also:

• SCALE
• SCALE (1) A

scale; when we approach the upper or See also:

• LOWER

lower limit of sensibility they become quite uncertain .