His work was mainly concerned with electricity and magnetism, though he also made some contributions to optics and physiology.
It was suggested again and again as each new discovery in electricity and magnetism seemed to render it more feasible.
Some of the principal phenomena of magnetism may be demonstrated with very little apparatus; much may be done with a small bar-magnet, a pocket compass and a few ounces of iron filings.
Electrostatics and Magnetism, p. 236.
This retardation was still more pronounced in the case of tungsten-steel, which lost its magnetism at 910° and remained nonmagnetic till it was cooled to 570°, a difference of 240°.
It is on the service that he rendered to science in establishing the relations between electricity and magnetism, and in developing the science of electromagnetism, or, as he called it, electrodynamics, that Ampere's fame mainly rests.
A bar of soft iron introduced into the coil is at once magnetized, the magnetism, however, disappearing almost completely as soon as the current ceases to flow.
An explanation of the twist has been given by Maxwell (Electricity and Magnetism, § 448).
He also engaged in work on magnetism, the polarization of light, phosphorescence and the absorption of light in crystals.
Within a limited space, such as that contained in a room, the field due to the earth's magnetism is sensibly uniform, the lines of force being parallel straight lines inclined to the horizon at the angle of dip, which at Greenwich in 1910 was about 67°.
In Englishspeaking countries the ore is commonly known as magnetite, and pieces which exhibit attraction as magnets; the cause to which the attractive property is attributed is called magnetism, a name also applied to the important branch of science which has been evolved from the study of phenomena associated with the magnet.
The distribution of magnetism and the position of the poles in magnets of other shapes, such as cylindrical or rectangular bars, cannot be specified by any general statement, though approximate determinations may be obtained experimentally in individual cases.'
If the iron is soft and fairly pure, it loses its attractive property when removed from the neighbourhood of the magnet; if it is hard, some of the induced magnetism is permanently retained, and the piece becomes an artificial magnet.
If the bar inserted into the coil is of hardened steel instead of iron, the magnetism will be less intense, but a larger proportion of it will be retained after the current has been cut off.
When the oscillations pass through the coil they annul the hysteresis and cause a change of magnetism within the coil connected to the telephone.
A more precise definition is the following: When the magnet is placed in a uniform field, the parallel forces acting on the positive poles of the constituent filaments, whether the filaments ' For the relations between magnetism and light see Magnetooptics.
The equation F = B 2 /87r is often said to express " Maxwell's law of magnetic traction " (Maxwell, Electricity and Magnetism,, §§ 642-646).
Maxwell, Electricity and Magnetism, § 7 H.
At a later period he was one of the leading contributors to the Encyclopaedia Britannica (seventh and eighth editions), the articles on Electricity, Hydrodynamics, Magnetism, Microscope, Optics, Stereoscope, Voltaic Electricity, &c., being from his pen.
Magnetism may be imparted to a bar of hardened steel by stroking it several times from end to end, always in the same direction, with one of the poles of a magnet.
Effects Of Mechanical Stress Upon Magnetization The effects of traction, compression and torsion in relation to magnetism have formed the subject of much patient investigation, especially at the hands of J.
upon the magnetism of iron, while the presence of only 2.25% was comparatively unimportant.
Steel articles, such as knitting or sewing needles and pieces of flat spring, may be readily magnetized by stroking them with the bar-magnet; after having produced magnetism in any number of other bodies, the magnet will have lost nothing of its own virtue.
Effects Of Temperature Upon Magnetism High Temperature.
Steel is much more retentive of magnetism than any ordinary iron, and some form of steel is now always used for making artificial magnets.
Joubert, Electricity and Magnetism, §§ 3 8 4, 39 6, 1226; A.
Denoting the distance AM by d 1, BM by d2, and AB by 1, we have for the force at M due to the magnetism of the rod H P =d 12 - horizontal component (dla - d 2 3).
(Maxwell, Electricity and Magnetism, II., § 437).
Inside a magnetized body, B is the force that would be exerted on a unit pole if placed in a narrow crevasse cut in the body, the walls of the crevasse being perpendicular to the direction of the magnetization (Maxwell, § § 399, 604); and its numerical value, being partly due to the free magnetism on the walls, is generally very different from that of H.
The fact being established that magnetism is essentially a molecular phenomenon, the next step is to inquire what is the constitution of a magnetic molecule, and why it is that some molecules are ferromagnetic, others paramagnetic, and others again diamagnetic. The best known of the explanations that have been proposed depend upon the magnetic action of an electric current.
Molecular Theory Of Magnetism According to W.
This experiment proves that the condition of magnetization is not confined to those parts where polar phenomena are exhibited, but exists throughout the whole body of the magnet; it also suggests the idea of molecular magnetism, upon which the accepted theory of magnetization is based.
"The earth," he adds elsewhere, "especially if fresh, has a certain magnetism in it, by which it attracts the salt, power, or virtue (call it either) which gives it life, and is the logic of all the labor and stir we keep about it, to sustain us; all dungings and other sordid temperings being but the vicars succedaneous to this improvement."
It was occasioned by the discharge of the Macedonian veterans, and only the personal magnetism of Alexander and his threat to entrust himself altogether to the Orientals availed to quell it.
Among other researches relating to atomic and molecular magnetism are those of 0.
An actual magnet may generally be regarded as a bundle of magnetic filaments, and those portions of the surface of the magnet where the filaments terminate, and socalled " free magnetism " appears, may be conveniently called poles or polar regions.
A magnet which consists entirely of such solenoids, having their ends either upon the surface or closed upon themselves, is called a solenoidal magnet, and the magnetism is said to be distributed solenoidally; there is no free magnetism in its interior.
The factor of proportionality will be I-41r, so that ' The principal theoretical investigations are summarized in Mascart and Joubert's Electricity and Magnetism, i.
69-94; Mascart and Joubert, Electricity and Magnetism, ii.
Thomson, Electricity and Magnetism, § 205.
Maxwell (Electricity and Magnetism, § 444), recognizing that the theory in this form gave no account of residual magnetization, made the further assumption that if the deflection of the axis of the molecule exceeded a certain angle, the axis would not return to its original position when the deflecting force was removed, but would retain a permanent set.
These observations have an important bearing upon the molecular theory of magnetism, which will be referred to later.
If a transverse cut is made through a bar whose magnetization is I and the two ends are placed in contact, it can be shown that this force is 27r I 2 dynes per unit of area (Mascart and Joubert, Electricity and Magnetism, § 322; and if the magnetization of the bar is due to an external field H produced by a magnetizing coil or otherwise, there is an additional force equal to HI.
In 1868 he obtained the same professorship at Edinburgh University, and in 1873 he published a textbook of Magnetism and Electricity, full of original work.
Hartog has endeavoured to show that it can only he formed by a dual force, analagous to that of magnetism, the spindle-fibi es being comparable to the lines of force in a magnetic field and possibly due to electrical differences in the cell.
Until 1820 all the artificial magnets in practical use derived their virtue, directly or indirectly, from the natural magnets found in the earth: it is now recognized that the source of all magnetism, not excepting that of the magnetic ore itself, is electricity, and it is usual to have direct recourse to electricity for producing magnetization, without the intermediary of the magnetic ore.
At shorter distances the magnetism induced in the weaker magnet will be stronger than its permanent magnetism, and there will be attraction; two magnets with their like poles in actual contact will always cling together unless the like poles are of exactly equal strength.
The opposite and parallel forces acting on the poles are always equal, a fact which is sometimes expressed by the statement that the total magnetism of a magnet is zero.
For many experiments the field due to the earth's magnetism is sufficient; this is practically quite uniform throughout considerable spaces, but its total intensity is less than half a unit.
an angle e with the normal, the normal component of the magnetization, I cos e, is called the surface density of the magnetism, and is generally denoted by a.
A magnet which can be divided into simple magnetic shells, either closed or having their edges on the surface of the magnet, is called a lamellar magnet, and the magnetism is said to be distributed lamellarly.
The force acting on the magnetism of one of the faces, and urging this face towards the other, will be less than B by 27r1, the part of the total force due to the first face itself; hence the force per unit of area with which the faces would press against each other if in contact is P = (B-27rI)I =27rT 2 +HI = (B 2 -H 2) =/81r.
The width of the gap may be diminished until it is no greater than the distance between two neighbouring molecules, when it will cease to be distinguishable, but, assuming the molecular theory of magnetism to be true, the above statement will still hold good for the intermolecular gap. The same pressure P will be exerted across any imaginary section of a magnetized rod, the stress being sustained by the intermolecular springs, whatever their physical nature may be, to which the elasticity of the metal is due.
The Magnetism of Ships.
A magnet can exert a force on some metals and this force is called magnetism.
The 10th series (1845) contains an account of his researches on the universal action of magnetism and diamagnetic bodies.
It also involves, of course, the distance between the needles and the distribution of the magnetism of the needles;: but this factor is determined by comparing the value given by the instrument, at a shore station, with that given by an ordinary magnetometer.
For a description of the method of using the Fox circle for observations at sea consult the Admiralty Manual of Scientific Inquiry, p. 116, while a description of the most recent form of the circle, known as the Lloyd-Creak pattern, will be found in Terrestrial Magnetism, 1901, 6, p. 119.
Bauer in Terrestrial Magnetism, 1906, II, p. 78.
of Books relating to Electricity and Magnetism, pp. 281-283; Royal Society's Cat.
The hull of an iron or steel ship is a magnet, and the distribution of its magnetism depends upon the direction of the ship's head when building, this result being produced by induction from the earth's magnetism, developed and impressed by the hammering of the plates and frames during the process of building.
The disturbance of the compass by the magnetism of the hull is generally modified, sometimes favourably, more often un favourably, by the magnetized fittings of the ship, such as masts, conning towers, deck houses, engines and boilers.
Soft iron is iron which becomes instantly magnetized by induction when exposed to any magnetic force, but has no power of retaining its magnetism.
Hard iron is less susceptible of being magnetized, but when once magnetized it retains its magnetism permanently.
If an iron ship be swung when upright for deviation, and the mean horizontal and vertical magnetic forces at the compass positions be also observed in different parts of the world, mathematical analysis shows that the deviations are caused partly by the permanent magnetism of hard iron, partly by the transient induced magnetism of soft iron both horizontal and vertical, and in a lesser degree by iron which is neither magnetically hard nor soft, but which becomes magnetized in the same manner as hard iron, though it gradually loses its magnetism on change of conditions, as, for example, in the case of a ship, repaired and hammered in dock, steaming in an opposite direction at sea.
This latter cause of deviation is called sub-permanent magnetism.
B has reference to horizontal forces acting in a longitudinal direction in the ship, and caused partly by the permanent magnetism of hard iron, partly by vertical induction in vertical soft iron either before or abaft the compass.
Thus the part of B caused by the permanent magnetism of hard iron must be corrected by permanent magnets horizontally placed in a fore and aft direction; the other part caused by vertical soft iron by means of bars of vertical soft iron, called Flinders bars, before or abaft the compass.
Although a compass may thus be made practically correct for a given time and place, the magnetism of the ship is liable to changes on changing her geographical position, and especially so when steaming at right angles or nearly so to the magnetic meridian, for then sub-permanent magnetism is developed in the hull.
Trials in certain ships showed that their magnetism consisted partly of hard iron, and the use of the plate was abandoned.
In this he gave equations resulting from the hypothesis that the magnetism of a ship is partly due to the permanent magnetism of hard iron and partly to the transient induced magnetism of soft iron; that the latter is proportional to the intensity of the inducing force, and that the length of the needle is infinitesimally small compared to the distance of the surrounding iron.
In 1855 the Liverpool Compass Committee began its work of investigating the magnetism of ships of the mercantile marine, resulting in three reports to the Board of Trade, all of great value, the last being presented in 1861.
See also Magnetism, and Navigation; articles on Magnetism of Ships and Deviations of the Compass, Phil.
In 1841 he found that he required rest, and it was not till 1845 that he entered on his second great period of research, in which he discovered the effect of magnetism on polarized light, and the phenomena of diamagnetism.
Before we describe this result we may mention that in 1862 he made the relation between magnetism and light the subject of his very last experimental work.
The first evidence which he obtained of the rotation of the plane of polarization of light under the action of magnetism was on the 13th of September 1845, the transparent substance being his own heavy glass.
In addition to a large number of publications in the Proceedings of the Royal Society and the Philosophical Magazine, he has published A Treatise on the Motion of Vortex Rings (1884); The Application of Dynamics to Physics and Chemistry (1886); Recent Researches in Electricity and Magnetism (1892); Elements of the Mathematical Theory of Electricity and Magnetism (18 95, 5th ed.
Tyndall's first original work in physical science was in his experiments with regard to magnetism and diamagnetic polarity, on which he was chiefly occupied from 1850 to 1855.
The original memoirs themselves on radiant heat and on magnetism were collected and issued as two large volumes under the following titles: Diamagnetism and Magne-crystallic Action (1870); Contributions to Molecular Physics in the Domain of Radiant Heat (1872).
Bouchotte have 1 See Lord Kelvin, Reprint of Papers on Electrostatics and Magnetism (1872);" Electrophoric Apparatus and Illustrations of Voltaic Theory,"p. 319;" On Electric Machines Founded on Induction and Convection,"p. 330;" The Reciprocal Electrophorus,"P. 337.
Clerk Maxwell, Treatise on Electricity and Magnetism (2nd ed., Oxford, 1881), vol.
But the indispensable qualities of iron did not shape man's evolution, because its great usefulness did not arise until historic times, or even, as in case of magnetism, until modern times.
excels, such as its strength, its magnetism, and the property which it alone has of being made at will extremely hard by sudden cooling and soft and extremely pliable by slow cooling; second, to the special combinations of useful properties in which it excels, such as its strength with its ready welding and shaping both hot and cold; and third, to the great variety of its properties.
When, in the course of centuries, the exhaustion of richer ores shall have forced us to mine, crush and concentrate mechanically or by magnetism the ores which contain only 2 or 3% of iron, then the cost of iron in the ore, measured in terms of the energy needed to mine and concentrate it, will be comparable with the actual cost of the copper in the ore of the copper-mines of to-day.
The general public were content to find the explanation of the movements in spirits, animal magnetism, odic force, galvanism, electricity, or even the rotation of the earth.
The connexion between aurora and earth magnetic disturbances renders it practically certain that if a 26-day or similar period exists in the one phenomenon it exists also in the other, and of the two terrestrial magnetism is probably the element least affected by external complications, such as the action of moonlight.
- Another auroral direction having apparently a close relation to terrestrial magnetism is the imaginary line drawn to the eye of an observer from the centre of the corona - i.e.
Relations to Magnetic Storms. - That there is an intimate connexion between aurora when visible in temperate latitudes and terrestrial magnetism is hardly open to doubt.
Anthropology treats of the mind in union with the body - of the natural soul - and discusses the relations of the soul with the planets, the races of mankind, the differences of age, dreams, animal magnetism, insanity and phrenology.
Perhaps the most original, and certainly the most permanent in their influence, were his memoirs on the theory of electricity and magnetism, which virtually created a new branch of mathematical physics.
In 1696 he was, although a zealous Tory, appointed deputy comptroller of the mint at Chester, and (August 19, 1698) he received a commission as captain of the "Paramour Pink" for the purpose of making extensive observations on the conditions of terrestrial magnetism.
In 1804 he had an opportunity of prosecuting his researches on air in somewhat unusual conditions, for the French Academy, desirous of securing some observations on the force of terrestrial magnetism at great elevations above the earth, through Berthollet and J.
At this height, with the thermometer marking 9 degrees below freezing, he remained for a considerable time, making observations not only on magnetism, but also on the temperature and humidity of the air, and collecting several samples of air at different heights.
It is magnetic, but loses its magnetism when heated, the loss being complete at about 34 0 -35 0 ° C. On the physical constants see H.
No better testimony to the value of the quaternion method could be desired than the constant use made of its notation by mathematicians like Clifford (in his Kinematic) and by physicists like ClerkMaxwell (in his Electricity and Magnetism).
Though he had not the personal magnetism of James G.
2 Verhandlungen der deutschen physikalischen Gesellschaft, 1899, 1, 147; or Terrestrial Magnetism, 1900, 5, 59.
Watson, Terrestrial Magnetism, 1901, 6, 187, describing magnetographs used in India; M.
Eschenhagen, Verhandlungen der deutschen physikalischen Gesellschaft, 1899, I, 147; Terrestrial Magnetism, 1900, 5, 59; and 1901, 6, 59; Zeits.
Cady, Terrestrial Magnetism, 1904, 9, 69, describing a declination magnetograph in which the record is obtained by means of a pen acting on a moving strip of paper, so that the curve can be consulted at all times to see whether a disturbance is in progress.
For descriptions of the arrangements adopted in some observatories see the following: U.S. observatories, Terrestrial Magnetism, 1903, 8, i 1 Utrecht, Terrestrial Magnetism, 1900, 5, 49; St Maur, Terrestrial Magnetism, 1898, 3, I Potsdam, Ver'offentlichungen des k.
Few of the leaders of either side could have stemmed the tide of defeat as he did at Stone river and turned a mere rally into a great victory as he did at Cedar Creek, by the pure force of personal magnetism.
Clerk Maxwell, Treatise on Electricity and Magnetism, vol.
interest in magnetism.
The oouple may be due to the earths magnetism, or to the torsion of a suspending wire, or to a bifilar suspension.
He never equalled Clay in the latter's magnetism of impulse and inspiration of affection, but he far surpassed him in clearness and directness and in tenacity of will.
The interconnexion of magnetism (which has an article to itself) and FIG.
electricity is discussed in Electromagnetism, and these manifestations in nature in Atmospheric Electricity; Aurora Polaris and Terrestrial magnetism.
Nobili (1784-1835) in 1825 conceived the ingenious idea of neutralizing the directive effect of the earth's magnetism by employing a pair of magnetized steel needles fixed to one axis, but with their magnetic poles pointing in opposite directions.
The study of the relation between the magnet and the circuit conveying an electric current then led Arago to the discovery of the " magnetism of rotation."
In 1855 he brought these researches to a conclusion by a general article on magnetic philosophy, having placed the whole subject of magnetism and electromagnetism on an entirely novel and solid basis.
His early contributions to electrostatics and electrometry are to be found described in his Reprint of Papers on Electrostatics and Magnetism (1872), and his later work in his collected Mathematical and Physical Papers.
Maxwell's electric and magnetic ideas were gathered together in a great mathematical treatise on electricity and magnetism which was published in 1873.1 This book stimulated in a most remarkable degree theoretical and practical research into the phenomena of electricity and magnetism.
This early work indicated that whilst there were a number of cases in which the square 1 A Treatise on Electricity and Magnetism (2 vols.), by James Clerk Maxwell, sometime professor of experimental physics in the university of Cambridge.
2 See Maxwell's Electricity and Magnetism, vol.
Recent Researches in Electricity and Magnetism (Oxford, 1892).
Clerk Maxwell, A Treatise on Electricity and Magnetism (2 vols., 3rd ed., 1892); id., Scientific Papers (2 vols., edited by Sir W.
Thomson, Recent Researches in Electricity and Magnetism (Oxford, 1893); id., Conduction of Electricity through Gases (Cambridge, 1903); id., Electricity and Matter (London, 1904); O.
Joubert, A Treatise on Electricity and Magnetism, English trans.
Porter, Electricity and Magnetism (London, 1903); A.
Gray, A Treatise on Magnetism and Electricity (London, 1898); H.
Burbury, The Mathematical Theory of Electricity and Magnetism (2 vols., 1885); Lord Kelvin (Sir William Thomson), Mathematical and Physical Papers (3 vols., Cambridge, 1882); Lord Rayleigh, Scientific Papers (q.
(Breslau, 1903 and 1905; a mine of wealth for references to original papers on electricity and magnetism from the earliest date up to modern times).
Forbes was especially interested in questions of heat, meteorology, and terrestrial magnetism, and it was to these that Stewart also mainly devoted himself.
In 1859 he was appointed director of Kew Observatory, and there naturally became interested in problems of meteorology and terrestrial magnetism.
He was the author of several successful textbooks of science, and also of the article on "Terrestrial Magnetism" in the ninth edition of this Encyclopaedia.
His investigations occupied almost the whole field of science, including physiology, physiological optics, physiological acoustics, chemistry, mathematics, electricity and magnetism, meteorology and theoretical mechanics.
The movable plate can be drawn down into a definite sighted position when a difference of potential is made between the two ' See Maxwell, Treatise on Electricity and Magnetism (2nd ed.), i.
Gray, Absolute Measurements in Electricity and Magnetism (London, 1888), vol.
Arago's fame as an experimenter and discoverer rests mainly on his contributions to magnetism and still more to optics.
This discovery, which gained him the Copley medal of the Royal Society in 1825, was followed by another, that a rotating plate of copper tends to communicate its motion to a magnetic needle suspended over it ("magnetism of rotation").
Ampere floated a voltaic battery with a coil of wire in its circuit in order to observe the effects of the earth's magnetism on the electric circuit.
In 1881 appeared his Elementary Lessons in Electricity and Magnetism, twice reprinted in 1882 and 16 times in the ensuing 12 years.
Gilbert's principal work is his treatise on magnetism, entitled De magnete, magneticisque corporibus, et de magno magnete tellure (London, 1600; later editions - Stettin, 1628, 1633; Frankfort, 1629, 1638).
Gilbert's is therefore not merely the first, but the most important, systematic contribution to the sciences of electricity and magnetism.
The five numbers of his Contributions to Electricity and Magnetism (1835-1842) were separately republished from the Transactions.
His first memoir on the theory of magnetism, Intensitas vis magneticae terrestris ad mensuram absolutam revocata, was published in 1833, and he shortly afterwards proceeded, in conjunction with Wilhelm Weber, to invent new apparatus for observing the earth's magnetism and its changes; the instruments devised by them were the declination instrument and the bifilar magnetometer.
Pye, brought him under further suspicion, and his revival of the powers of convocation lessened his influence at court; but his unfailing tact and wide sympathies, his marvellous energy in church organization, the magnetism of his personality, and his eloquence both on the platform and in the pulpit, gradually won for him recognition as without a rival on the episcopal bench.
Details of his experimental work in magnetism and the problems of electricity and light are given in 17.3 8 9, 39 1 and 346, 6.859, 9.206, 21.936.
Another discussed conduction in curved sheets; a third the distribution of electricity in two influencing spheres; a fourth the deter mination of the constant on which depends the intensity of induced currents; while others were devoted to Ohm's law, the motion of electricity in submarine cables, induced magnetism, &c. In other papers, again, various miscellaneous topics were treated - the thermal conductivity of iron, crystalline reflection and refraction, certain propositions in the thermodynamics of solution and vaporization, &c. An important part of his work was contained in his Vorlesungen fiber mathematische Physik (1876), in which the principles of dynamics, as well as various special problems, were treated in a somewhat novel and original manner.
He studied the reflection and polarization of radiant heat, the magnetism of rocks, electrostatic induction, daguerrotypy, &c.
He published numerous works on different branches of physics, including A Complete Treatise on Electricity (1777), Treatise on the Nature and Properties of Air and other permanently Elastic Fluids (1781), History and Practice of Aerostation (1785), Treatise on Magnetism (1787), Elements of Natural and Experimental Philosophy (1803), Theory and Practice of Medical Electricity (1780), and Medical Properties of Factitious Air (1798).
During the Civil War, however, he was promoted too early and rapidly for his own good, and the strong personal magnetism he inspired while so young developed qualities injurious to a full measure of success and usefulness, despite his great opportunities.
Gray, Absolute Measurements in Electricity and Magnetism (1900); Rollo Appleyard, " The Conductometer," Proc. Phys.
Although Adams's researches on Neptune were those which attracted widest notice, the work he subsequently performed in relation to gravitational astronomy and terrestrial magnetism was not less remarkable.
The determination of the constants in Gauss's theory of terrestrial magnetism occupied him at intervals for over forty years.
This important ore of iron is most celebrated for its magnetic properties (see Magnetism and Compass), but the mineral is not always magnetic, although invariably attracted by a magnet.
Aepinus is best known by his researches, theoretical and experimental, in electricity and magnetism, and his principal work, Tentamen Theoriae Electricitatis et Magnetismi, published at St Petersburg in 1759, was the first systematic and successful attempt to apply mathematical reasoning to these subjects.
Misled, however, into identifying it with magnetism, he imagined circulation in the solar system to be maintained through the material compulsion of fibrous emanations from the sun, carried round by his axial rotation.
Evidence is also accumulating to show that the sun and stars are radio-active bodies, and that emanations proceeding from the sun, and reaching the earth, have important relations to the phenomena of Terrestrial Magnetism and the Aurora.
In the meanwhile the compass went through a process of complete reconstruction in his hands, a process which enabled both the permanent and the temporary magnetism of the ship to be readily compensated, while the weight of the bo-in.
A number of his scientific papers were collected in his Reprint of Papers on Electricity and Magnetism (1872), and in his Mathematical and Physical Papers (1882, 1883 and 1890), and three volumes of his Popular Lectures and Addresses appeared in 1889-1894.
declinare, to decline), in magnetism the angle between true north and magnetic north, i.e.
(See Terrestrial magnetism.) In astronomy the declination is the angular distance, as seen from the earth, of a heavenly body from the celestial equator, thus corresponding with terrestrial latitude.
He also carried on extensive researches in the theory of magnetism; and it is interesting that in connexion with his observations in terrestrial magnetism he not only employed an early form of mirror galvanometer, but also, about 1833, devised a system of electromagnetic telegraphy, by which a distance of some 9000 ft.
captivated instantly by his magnetism.
It also discusses electromagnetism, Solar magnetism, dynamo theory, ocean floor magnetization, and the magnetospheres of the Earth and the planets.
The German physicist and chemist studied electricity and magnetism, and designed a mirror galvanometer.
Colin Wilson had suggested I link my charcoal data with his temperature data, which used remnant magnetism.
They have a magnetism that has the power to draw us.
Magnetic susceptibility relates to the induced magnetism of a material when in the presence of a magnetic field.
They explain that magnetism generally attracts particles into the atmosphere, drawing them into the area around the pylons.
In April 1839, being the obvious choice James Clark Ross was appointed to command the expedition investigating terrestrial magnetism in Antarctica.
Many of these other parameters are also directly affected by magnetism.
Applications include the measurement of induced and remanent magnetism and use in site surveys prior to the installation of MRI equipment.
The compass revealed nothing of the nature of terrestrial magnetism to the medieval thinker.
Why she couldn't have stuck to finding more viruses like luck and sexual magnetism is anyone's guess.
A copy of the program can be downloaded as a PDF file and contains an introduction to molecular magnetism.
animal magnetism that dances like iron filings at the North Pole.
Furthermore the remaining permanent magnetism might be quickly shaken out.
Research here has determined that there was a variation of 120° in earth magnetism some 30,000 years ago.
In 1775 Franz Mesmer developed healing by animal magnetism which was later renamed hypnosis.
The subject of rock magnetism and paleomagnetism is outwith the scope of this article.
Research My research in rock and mineral magnetism focuses on the assessment of the reliability of geomagnetic field recorders.
To be sure, the magnitude of the earth's magnetism has been dropping for a long time.
magnetism of rocks to help locate oil deposits.
The use of low energy muons is a rapidly developing field with great potential for the study of magnetism near surfaces.
We only use the highest grade neodymium healing magnets, which keep their magnetism for ten years.
Wyn Williams uses powerful computer facilities for intensive numerical modeling of the underlying physics of magnetism in mineral grains.
remanent magnetism and use in site surveys prior to the installation of MRI equipment.
However, electron spin is very familiar to us in another way -- it's at the heart of magnetism.
Gauss in his theory of terrestrial magnetism.
2; P.T., " Philosophical Transactions Royal Society of London "; T.M., Terrestrial Magnetism, edited by Dr L.
Passing briefly over the conclusions arrived at in the Meditations, it deals in its second, third and fourth parts with the general c l principles of physical science, especially the laws of motion, with the theory of vortices, and with the phenomena of heat, light, gravity, magnetism, electricity, &c., upon the earth.
If Descartes had contented himself with thus explaining the phenomena of gravity, heat, magnetism, light and similar forces by means of the molecular movements of his vortices, even such a theory would have excited admiration.
Numerous other papers on molecular physics, including an experimental research on magnetism, appeared in the Proceedings of the Russian Academy of Science, the Physikalische Zeitschrift, the Proceedings of the German Physical Society, the Annalen der Physik, etc. (F.
15) is worked from a relay, the dying away of the magnetism in the iron cores of the electromagnet, when the relay tongue moves from the Spark marking to the spacing side, i.e.
During the passage of the Telegraph Bill 1878 through parliament the Postmaster-General endeavoured, without success, to insert a clause declaring that the term " telegraph " included " any apparatus for transmitting messages or other communications with the aid of electricity, magnetism, or any other like agency.
MAGNETITE, a mineral forming the natural magnet (see Magnetism), and important also as an iron-ore.
Gray, Absolute Measurements in Electricity and Magnetism, vol.
(See also Electro Magnetism, Terrestrial Magnetism, Magneto-Optics and Units.) I.
(See Terrestrial Magnetism.) difficulty was overcome by C. A.
Within a limited space, such as that contained in a room, the field due to the earth's magnetism is sensibly uniform, the lines of force being parallel straight lines inclined to the horizon at the angle of dip, which at Greenwich in 1910 was about 67Ã‚°.
The field-strength at any point is also called the magnetic force at that point; it is denoted by H, or, when it is desired to draw attention to the fact that it is a vector quantity, by the block letter H, or the German character, C. Magnetic force is sometimes, and perhaps more suitably, termed magnetic intensity; it corresponds to the intensity of gravity g in the theory of heavy bodies (see Maxwell, Electricity and Magnetism, § 12 and § 68, footnote).
This retardation was still more pronounced in the case of tungsten-steel, which lost its magnetism at 910Ã‚° and remained nonmagnetic till it was cooled to 570Ã‚°, a difference of 240Ã‚°.
Useful instructions have been furnished by Carl Barus (Terrestrial Magnetism, 1897, 2, II) for the preparation of magnets calculated to withstand the effects of time, percussion and ordinary temperature variations.
This illustrates the first stage in the process of magnetization, when the moment is proportional to the field and there is no hysteresis or residual magnetism (see ante).
Coulomb's researches provided data for the development of a mathematical theory of magnetism, which was indeed initiated by himself, but was first treated in a complete form by Poisson in a series of memoirs published in 1821 and later.
The valuable work of Gauss on magnetic theory and measurements, especially in relation to terrestrial magnetism, was published in his Intensitas vis magneticae terrestris, 1833, and in memoirs communicated to the Resultate aus den Beobachtungen des magnetischen Vereins, 1838 and 1839, which, with others, are contained in vol.
The application of the theory by P. Langevin to the case of molecular magnetism has been noticed above, and there can be little doubt that in the near future it will contribute to the solution of other problems which are still obscure.
to xxxii., including accounts of some interesting experiments in magnetism and capillary attraction.
For the proof of the converse proposition we must refer the reader to the Electrical Researches of Cavendish, p. 419, or to Maxwell's Treatise on Electricity and Magnetism, 2nd ed., vol.
The core of the electromagnet is worked at a point far below magnetic saturation (see Magnetism); hence the field is nearly proportional to the square of the current, and the resistance offered to the rotating mercury by the friction against the sides of the cavity is nearly proportional to the square of the speed.
In order to overcome the friction of the counting train, Ferranti ingeniously gave to the core of the electromagnet a certain amount of permanent magnetism.
'The following are the more important of his works in addition to the two already mentioned: - Considerations touching the Usefulness of Experimental Natural Philosophy (1663), followed by a second part in 1671; Experiments and Considerations upon Colours, with Observations on a Diamond that Shines in the Dark (1663); New Experiments and Observations upon Cold (1665); Hydrostatical Paradoxes (1666); Origin of Forms and Qualities according to the Corpuscular Philosophy (1666); a continuation of his work on the spring of air (1669); tracts about the Cosmical Qualities of Things, the Temperature of the Subterraneal and Submarine Regions, the Bottom of the Sea, &c. with an Introduction to the History of Particular Qualities (1670); Origin and Virtues of Gems (1672); Essays of the strange Subtilty, great Efficacy, determinate Nature of Effluviums (1673); two volumes of tracts on the Saltness of the Sea, the Hidden Qualities of the Air, Cold, Celestial Magnets, Animadversions on Hobbes's Problemata de Vacuo (1674); Experiments and Notes about the Mechanical Origin or Production of Particular Qualities, including some notes on electricity and magnetism (1676); Observations upon an artificial Substance that Shines without any Preceding Illustration (1678); the Aerial Noctiluca 0680); New Experiments and Observations upon the Icy Noctiluca (1682) a further continuation of his work on the air; Memoirs for the Natural History of the Human Blood (1684); Short Memoirs for the Natural Experimental History of Mineral Waters (1685); Medicina Hydrostatica (1690); and Experimenta et Observationes Physicae (1691).
The elements which are actually measured when determining the value of the earth's field are usually the declination, the dip and the horizontal component (see Terrestrial magnetism).
(See C. Bergen, Terrestrial Magnetism, 1896, i.
Young (see Brande's Quarterly Journal, 1820) investigated mathematically the magnetism of ships.
Birkeland, Expedition norvegienne 1899-1900 pour l'etude des aurores boreales (Christiania, 1901); (20) Terrestrial Magnetism, vol.
438; (23) Expedition polaire finlandaise (1882-1884), tome iii.; (24) Charles Nordmann, Theses presentees a la Faculte des Sciences de Paris (1903); (25) Terrestrial Magnetism, vol.
It is magnetic, but loses its magnetism when heated, the loss being complete at about 34 0 -35 0 Ã‚° C. On the physical constants see H.
MAGNETOGRAPH, an instrument for continuously recording the values of the magnetic elements, the three universally chosen being the declination, the horizontal component and the vertical component (see Terrestrial Magnetism).
In 1908 ten departments had been organized: Botanical Research, with a "desert laboratory" (1903) at Tucson, Arizona; Economics and Sociology (1904); Experimental Evolution, with a station (1904) at Cold Spring Harbor, New York (see Huntington, N.Y.); Geophysical Research, with a laboratory (1906-1907) at Washington - investigations have been carried on by the U.S. Geological Survey and at McGill University, Toronto; Historical Research (1903); Marine Biology, with a laboratory (1904) at Tortugas, Florida; Meridian Astrometry (1906; work is carried on especially at Dudley Observatory, Albany, New York); Research in Nutrition, with a laboratory (1906) at Boston, Massachusetts - investigations (since 1904) had been carried on at Yale and Wesleyan universities; Solar Physics, with observatory (1905) on Mount Wilson, California, and workshops at Pasadena, California, and Terrestrial Magnetism (1903; headquarters in Washington); the institution had assisted Luther Burbank in his horticultural experiments since 1905, and had published the Index Medicus since 1903; and it makes occasional grants for minor research and tentative investigations.
Faraday, " On some new Electro-Magnetical Motions and on the Theory of Magnetism," Quarterly Journal of Science, 1822, 12, p. 74; or Experimental Researches on Electricity, vol.
Accordingly when he sprinkled iron filings on a card held over a magnet and revealed the curvilinear system of lines of force (see Magnetism), he regarded these fragments of iron as simple indicators of a physical state in the space already in existence round the magnet.
The conclusion to which the above observers came was that any quadrant electrometer made in any manner does not See Maxwell, Electricity and Magnetism (2nd ed., Oxford, 1881), vol.
Kepler divined its possibility; but his thoughts, derailed (so to speak) by the false analogy of magnetism, brought him no farther than to the .rough draft of the scheme of vortices expounded in detail by Rene Descartes in his Principia Philosophiae (1644).
Firstly, he brought about the final consolidation of electricity and magnetism into a single self-consistent theory of electromagnetism.
However, electron spin is very familiar to us in another way -- it 's at the heart of magnetism.
"There was a palpable magnetism between Julio and the audience, and not just the women-men and women."
This means you can wear one with complete confidence that you won't stand out from the crowd for anything other than your own personal magnetism.
These principles, namely the Law of Attraction, the Law of Magnetism, etc., are actually real principles and phenomena that take place in the universe by way of quantum physics.
You have a certain animal magnetism that naturally draws people to you, and while you can be the life of the party when you choose, you value time spent alone.
The mischievous teen's magnetism allows him the ability to get people to do what he wants, no questions asked.
Other features include helium escape valve for saturation diving, a soft iron secondary inner case to protect the movement from magnetism, and two shock resistant safety systems.
Planet Online: Here is a pair of RocketWear's Animal Magnetism Print capri pajama set.
This is insignificant compared to the size of the currents which several authorities have calculated from considerations as to terrestrial magnetism.
He carried out a number of magnetic investigations which resulted in the discovery of many interesting phenomena, some of which have been rediscovered by others; they related among other things to the effect of mechanical strain on the magnetic properties of the magnetic metals, to the relation between the chemical composition of compound bodies and their magnetic properties, and to a curious parallelism between the laws of torsion and of magnetism.
But the theory, in a fully developed form, first appeared in 1873 in his great treatise on Electricity and Magnetism.
" Thomson and Tait," as it is familiarly called ("T and T" was the authors' own formula), was planned soon after Lord Kelvin became acquainted with Tait, on the latter's appointment to his professorship in Edinburgh, and it was intended to be an all-comprehensive treatise on physical science, the foundations being laid in kinematics and dynamics, and the structure completed with the properties of matter, heat, light, electricity and magnetism.
By far the greater and more important part of his work related to electricity and magnetism.
He carried this tendency to mysticism into his physical researches, and was led by it to take a deep interest in the phenomena of animal magnetism.
Effects of Temperature on Magnetism.
Molecular Theory of Magnetism.
This may be shown by means of the uniform field of force due to the earth's magnetism.
The dimensions of a piece of iron, for example, its elasticity, its thermo-electric power and its electric conductivity are all changed under the influence of magnetism.
So long as the wire (supposed isotropic) is free from torsional stress, there will be no external evidence of magnetism.
Therefore and m = v I - 'm of d22 (47) constant cell B21 its object is to produce inside the tube a magnetic field equal and opposite to that due to the earth's magnetism.
Weber's theory of molecular magnetism.
The strength of the induced current is - HScosO/L, where 0 is the inclination of the axis of the circuit to the direction of the field, and L the coefficient of self-induction; the resolved part of the magnetic moment in the direction of the field is equal to - HS 2 cos 2 6/L, and if there are n molecules in a unit of volume, their axes being distributed indifferently in all directions, the magnetization of the substance will be-3nHS 2 /L, and its susceptibility - 3S 2 /L (Maxwell, Electricity and Magnetism, § 838).
There are strong reasons for believing that magnetism is a phenomenon involving rotation, and as early as 1876 Rowland, carrying out an experiment which had been proposed by Maxwell, showed that a revolving electric charge produced the same magnetic effects as a current.
Since that date it has more than once been suggested that the molecular currents producing magnetism might be due to the revolution of one or more of the charged atoms or " ions " constituting the molecule.
It has been supposed that certain electrons revolve like satellites in orbits around the atoms with which they are associated, a view which receives strong support from the phenomena of the Zeeman effect, and on this assumption a theory has been worked out by P. Langevin, 2 which accounts for many, of the observed facts of magnetism.
The foundations of the modern science of magnetism were laid by William Gilbert.
Thomson, Electricity and Magnetism, § 132.
Regarding it as important that all reasoning with reference to magnetism should be conducted without any uncertain assumptions, he worked out a mathematical theory upon the sole foundation of a few wellknown facts and principles.
Ampere's experimental and theoretical investigation of the mutual action of electric currents, and of the equivalence of a closed circuit to a polar magnet, the latter suggesting his celebrated hypothesis that molecular currents were the cause of magnetism.
For outlines of the mathematical theory of magnetism and references see H.
on the principle of powerful magnetism and feeble galvanism " which is believed to have constituted the first actual electromagnet.
Another was the magnetic rotation of the plane of polarization of light, which was effected in 1845, and for the first time established a relation between light and magnetism.
In 1873 James Clerk Maxwell published his classical Treatise on Electricity and Magnetism, in which Faraday's ideas were translated into a mathematical form.
Ann., 1888, 34, 1 55, 55 1, 609; and later vols.) they have commanded universal assent, and his methods are adopted in all modern work on electricity and magnetism.
Thomson (Lord Kelvin), Reprint of Papers on Electrostatics and Magnetism (London, 1884, containing papers on magnetic theory originally published between 1844 and 1855, with additions); J.
C. Maxwell, Treatise on Electricity and Magnetism (3rd ed., Oxford, 1892); E.
Induction in Iron and other Metals (3rd ed., London, 2900); Thomson, Recent Researches in Electricity and Magnetism (Oxford, 2893); Elements of Mathematical Theory of Electricity and Magnetism 3rd ed., Cambridge, 1904); H.
Gray, Treatise on Magnetism and Electricity, vol.
Porter, Treatise on Electricity and Magnetism (London, 1903); A.
Terrestrial magnetism >>
They relate almost entirely to electrical phenomena, such as the magnetic rotation of light, the action of gas batteries, the effects of torsion on magnetism, the polarization of electrodes, &c., sufficiently complete accounts of which are given in Wiedemann's Galvanismus.
Stern, on terrestrial magnetism by Goldschmidt, and on the method of least squares by K.
Clerk Maxwell, Electricity and Magnetism, ii.
By his discovery that the attracting force in any direction of a mass upon a particle could be obtained by the direct process of differentiating a single function, Laplace laid the foundations of the mathematical sciences of heat, electricity and magnetism.
In the figure of the earth, the theory of attractions, and the sciences of electricity and magnetism this powerful calculus occupies a prominent place.
His name is best known in connexion with electricity and magnetism.
But in regard to their power of retaining their magnetism none of them comes at all up to the compound metal steel.
The investigations on magnetism led to the important practical discovery of a means of rectifying or compensating compass errors in ships.
Coulomb is distinguished in the history alike of mechanics and of electricity and magnetism.
(See MAGNETISM, TERRESTRIAL.)
Assoc. Report for 1867, or Lord Kelvin's Reprint of Papers on Electrostatics and Magnetism, p. 260.
It is not even necessary that 2 See Maxwell, Treatise on Electricity and Magnetism (3rd ed., Oxford, 1892), vol.
The reader is also referred to an article by Lord Kelvin (Reprint of Papers on Electrostatics and Magnetism, p. 178), entitled " Determination of the Distribution of Electricity on a Circular Segment of a Plane, or Spherical Conducting Surface under any given Influence," where another equivalent expression is given for the capacity of an ellipsoid.
See Maxwell, Electricity and Magnetism, vol.
Ann., 18J4, 91; see also Maxwell, Electricity and Magnetism, vol.
The above is a statement of Coulomb's law, that the electric fores at the surface of a conductor is proportional to the surface density of the charge at that point and equal to 41r times the density.3 See Maxwell, Electricity and Magnetism, vol.
Hence that distribution of potential which is neces 1 See Maxwell, Electricity and Magnetism, vol.
(26), that distribution, together with the point-charge +q at A, will make a distribution of electric force at all points outside the sphere 2 See Lord Kelvin's Papers on Electrostatics and Magnetism, p. 144.
Thomson, Elements of the Mathematical Theory of Electricity and Magnetism (Cambridge, 1895); J.
Porter, Elementary Treatise on Electricity and Magnetism (London, 1903); S.
P. Thompson, Elementary Lessons on Electricity and Magnetism (London, 1903).
Clerk Maxwell, A Treatise on Electricity and Magnetism (1st ed., Oxford, 1873; 2nd ed.
Thomson, 1892); Joubert and Mascart, Electricity and Magnetism, English translation by E.
Atkinson (London, 1883); Watson and Burbury, The Mathematical Theory of Electricity and Magnetism (Oxford, 188.5); A.
Gray, A Treatise on Magnetism and Electricity (London, 1898).
Long previously Lord Kelvin himself came nearer this view, in offering the opinion that magnetism consisted, in some way, in the angular momentum of the material molecules, of which the energy of irregular translations constitutes.
A dielectric substance is electrically polarized by a field of electric force, the atomic poles being made up of the displaced positive and negative intrinsic charges in the atom: the polarization per unit volume (f',g',h') may be defined on the analogy of magnetism, and d/dt(f',g',h') thus constitutes true electric current of polarization, i.e.
But in the transition from molecular theory to the electrodynamics of extended media, all magnetism has to be replaced by a distribution of current; the latter being now specified by volume as well as by flow so that (u,v,w) ST is the current in the element of volume 6T.
Gray, Absolute Measurements in Electricity and Magnetism (1900); E.
Becoming interested in terrestrial magnetism he made many observations of magnetic intensity and declination in various parts of Sweden, and was charged by the Stockholm Academy of Sciences with the task, not completed till shortly before his death, of working out the magnetic data obtained by the Swedish frigate "Eugenie" on her voyage round the world in 1851-1853.
The dynamical series of stages in nature, the forms in which the ideal structure of nature is realized, are matter, as the equilibrium of the fundamental expansive and contractive forces; light, with its subordinate processes - magnetism, electricity, and chemical action; organism, with its component phases of reproduction, irritability and sensibility.'
He was a man of fine appearance and courtly manners, and he possessed personal magnetism and the ability to make friends, two qualities that contributed in great measure to his success.
The manuscript residue includes papers on atmospheric refraction (dated 1755), on the motion of Mars as affected by the perturbations of Jupiter and the Earth (1756), and on terrestrial magnetism (1760 and 1762).
Passing from Moleschott to Lyell's view of the evolution of the earth's crust and later to Darwin's theory of natural selection and environment, he reached the general inference that, not God but evolution of matter, is the cause of the order of the world; that life is a combination of matter which in favourable circumstances is spontaneously generated; that there is no vital principle, because all forces, non-vital and vital, are movements; that movement and evolution proceed from life to consciousness; that it is foolish for man to believe that the earth was made for him, in the face of the difficulties he encounters in inhabiting it; that there is no God, no final cause, no immortality, no freedom, no substance of the soul; and that mind, like light or heat, electricity or magnetism, or any other physical fact, is a movement of matter.
(e) Newton in the Principia, repeating and correcting Wren's experiments on collision, and adding further instances from attractive forces of magnetism and gravity, induced the third law of motion as a general law of all forces.
Withdraw this foundation of bodies as inter-resisting forces causing one another in collision to form a joint mass with a common velocity but without penetration, and the evidence of the third law disappears; for in the case of attractive forces we know nothing of their modus operandi except by the analogy of the collision of inter-resisting bodies, which makes us believe that something similar, we know not what, takes place in gravity, magnetism, electricity, &c. Now, Mach, though he occasionally drops hints that the discovery of the law of collision comes first, yet never explains the process of development from it to the third law of motion.
MAGNETOMETER, a name, in its most general sense, for any instrument used to measure the strength of any magnetic field; it is, however, often used in the restricted sense of an instrument for measuring a particular magnetic field, namely, that due to the earth's magnetism, and in this article the instruments used for measuring the value of the earth's magnetic field will alone be considered.
Omitting correction terms depending on the temperature and on the inductive effect of the earth's magnetism on the moment of the deflecting magnet, if 0 is the angle which the axis of the deflected magnet makes with the meridian when the centre of the deflecting magnet is at a distance r, then zM sin B=I+P+y2 &c., in which P and Q are constants depending on the dimensions and magnetic states of the two magnets.
Fraser, Terrestrial Magnetism, 1901, 6, p. 65, containing a description of a modified Kew pattern unifilar as used in the Indian survey; H.
The magnetism of these two needles is never reversed, and they are as much as possible protected from shock and from approach to other magnets, so that their magnetic state may remain as constant as possible.
The Memoirs of the Berlin Academy from 1761 to 1784 contain many of his papers, which treat of such subjects as resistance of fluids, magnetism, comets, probabilities, the problem of three bodies, meteorology, &c. In the Acta Helvetica (1752-1760) and in the Nova acta erudita (1763-1769) several of his contributions appear.
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