Question: When was it proposed that electricity and magnetism were distinct effects by scientists William Gilbert?
About the article "Electromagnetism", section "Classical electrodynamics".

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Various scientists proposed that electricity and magnetism were linked.
Around 1800 Alessandro Volta developed the first means of producing an electrical current.
In 1802 Gian Domenico Romagnosi may have suggested a relationship between electricity and magnetism but his reports went unnoticed.
In 1820 Hans Christian Ørsted performed a simple and today widely known experiment on electric current and magnetism.
He demonstrated that a wire carrying a current could deflect a magnetized compass needle.
Ørsted's work influenced André-Marie Ampère to produce a theory of electromagnetism.
Several scientists speculated that light might be connected with electricity or magnetism.
Around 1830 Francesco Zantedeschi suggested a connection between light, electricity, and magnetism.
In 1831, Michael Faraday began a series of experiments in which he discovered electromagnetic induction.
The relation was mathematically modelled by Faraday's law, which subsequently became one of the four Maxwell equations.
Faraday proposed that electromagnetic forces extended into the empty space around the conductor, but did not complete his work involving that proposal.
In 1846 Michael Faraday speculated that light was a wave disturbance in a force field".
In 1832 Joseph Henry performed experiments detecting inductive magnetic effects over a distance of .
He was the first (1838–42) to produce high frequency AC electrical oscillations, and to point out and experimentally demonstrate that the discharge of a capacitor under certain conditions is oscillatory, or, as he puts it, consists ""of a principal discharge in one direction and then several reflex actions backward and forward, each more feeble than the preceding until equilibrium is attained"".
This view was also later adopted by Helmholtz, but the mathematical demonstration of this fact was first given by Lord Kelvin in his paper on "Transient Electric Currents". 
The 16th century marked the beginning of scientific understanding of electricity and magnetism that culminated with the production of electric power and the industrial revolution in the late 19th century.
In the 1550s, English scientist William Gilbert spent 17 years experimenting with magnetism and, to a lesser extent, electricity.
For his work on magnets, Gilbert became known as "The Father of Magnetism."
His book "De Magnete" quickly became the standard work throughout Europe on electrical and magnetic phenomena.
He made the first clear distinction between magnetism and what was then called the "amber effect" (static electricity).
In 1663, German physicist Otto von Guericke created the first electrostatic generator, which produced static electricity by applying friction.
The generator was made of a large sulfur ball inside a glass globe, mounted on a shaft.
The ball was rotated by means of a crank and a static electric spark was produced when a pad was rubbed against the ball as it rotated.
The globe could be removed and used as an electrical source for experiments with electricity.
Von Guericke used his generator to show that like charges repelled each other. 
The scientist William Gilbert proposed, in his "De Magnete" (1600), that electricity and magnetism, while both capable of causing attraction and repulsion of objects, were distinct effects.
Mariners had noticed that lightning strikes had the ability to disturb a compass needle, but the link between lightning and electricity was not confirmed until Benjamin Franklin's proposed experiments in 1752.
One of the first to discover and publish a link between man-made electric current and magnetism was Romagnosi, who in 1802 noticed that connecting a wire across a voltaic pile deflected a nearby compass needle.
However, the effect did not become widely known until 1820, when Ørsted performed a similar experiment.
Ørsted's work influenced Ampère to produce a theory of electromagnetism that set the subject on a mathematical foundation.
A theory of electromagnetism, known as classical electromagnetism, was developed by various physicists over the course of the 19th century, culminating in the work of James Clerk Maxwell, who unified the preceding developments into a single theory and discovered the electromagnetic nature of light.
In classical electromagnetism, the electromagnetic field obeys a set of equations known as Maxwell's equations, and the electromagnetic force is given by the Lorentz force law.
One of the peculiarities of classical electromagnetism is that it is difficult to reconcile with classical mechanics, but it is compatible with special relativity.
According to Maxwell's equations, the speed of light in a vacuum is a universal constant, dependent only on the electrical permittivity and magnetic permeability of free space.
This violates Galilean invariance, a long-standing cornerstone of classical mechanics.
One way to reconcile the two theories (electromagnetism and classical mechanics) is to assume the existence of a luminiferous aether through which the light propagates.
However, subsequent experimental efforts failed to detect the presence of the aether.
After important contributions of Hendrik Lorentz and Henri Poincaré, in 1905, Albert Einstein solved the problem with the introduction of special relativity, which replaces classical kinematics with a new theory of kinematics that is compatible with classical electromagnetism.
(For more information, see History of special relativity.
)In addition, relativity theory shows that in moving frames of reference a magnetic field transforms to a field with a nonzero electric component and vice versa; thus firmly showing that they are two sides of the same coin, and thus the term "electromagnetism".
(For more information, see Classical electromagnetism and special relativity and Covariant formulation of classical electromagnetism.
Benjamin Franklin is frequently confused as the key luminary behind electricity; William Watson and Benjamin Franklin share the discovery of electrical potentials.
Benjamin Franklin promoted his investigations of electricity and theories through the famous, though extremely dangerous, experiment of flying a kite through a storm-threatened sky.
A key attached to the kite string sparked and charged a Leyden jar, thus establishing the link between lightning and electricity.
Following these experiments, he invented a lightning rod.
It is either Franklin (more frequently) or Ebenezer Kinnersley of Philadelphia (less frequently) who is considered to have established the convention of positive and negative electricity.
Theories regarding the nature of electricity were quite vague at this period, and those prevalent were more or less conflicting.
Franklin considered that electricity was an imponderable fluid pervading everything, and which, in its normal condition, was uniformly distributed in all substances.
He assumed that the electrical manifestations obtained by rubbing glass were due to the production of an excess of the electric fluid in that substance and that the manifestations produced by rubbing wax were due to a deficit of the fluid.
This theory was opposed by Robert Symmer's "Two-fluid" theory in 1759.
By Symmer's theory, the vitreous and resinous electricities were regarded as imponderable fluids, each fluid being composed of mutually repellent particles while the particles of the opposite electricities are mutually attractive.
When the two fluids unite as a result of their attraction for one another, their effect upon external objects is neutralized.
The act of rubbing a body decomposes the fluids, one of which remains in excess on the body and manifests itself as vitreous or resinous electricity.
Up to the time of Franklin's historic kite experiment, the identity of the electricity developed by rubbing and by electrostatic machines (frictional electricity) with lightning had not been generally established.
Dr. Wall, Abbot Nollet, Hauksbee, Stephen Gray and John Henry Winkler had indeed suggested the resemblance between the phenomena of "electricity" and "lightning", Gray having intimated that they only differed in degree.
It was doubtless Franklin, however, who first proposed tests to determine the sameness of the phenomena.
In a letter to Peter Comlinson of London, on 19 October 1752, Franklin, referring to his kite experiment, wrote,On 10 May 1742 Thomas-François Dalibard, at Marley (near Paris), using a vertical iron rod 40 feet long, obtained results corresponding to those recorded by Franklin and somewhat prior to the date of Franklin's experiment.
Franklin's important demonstration of the sameness of frictional electricity and lightning doubtless added zest to the efforts of the many experimenters in this field in the last half of the 18th century, to advance the progress of the science.
Franklin's observations aided later scientists such as Michael Faraday, Luigi Galvani, Alessandro Volta, André-Marie Ampère and Georg Simon Ohm, whose collective work provided the basis for modern electrical technology and for whom fundamental units of electrical measurement are named.
Others who would advance the field of knowledge included William Watson, Boze, Smeaton, Louis Guillaume Le Monnier, Jacques de Romas, Jean Jallabert, Giovanni Battista Beccaria, Tiberius Cavallo, John Canton, Robert Symmer, Abbot Nollet, John Henry Winkler, Richman, Dr. Wilson, Kinnersley, Joseph Priestley, Franz Aepinus, Edward Hussey Délavai, Henry Cavendish and Charles-Augustin de Coulomb.
Descriptions of many of the experiments and discoveries of these early electrical scientists may be found in the scientific publications of the time, notably the "Philosophical Transactions", "Philosophical Magazine", "Cambridge Mathematical Journal", "Young's Natural Philosophy", Priestley's "History of Electricity", Franklin's "Experiments and Observations on Electricity", Cavalli's "Treatise on Electricity" and De la Rive's "Treatise on Electricity".
Henry Elles was one of the first people to suggest links between electricity and magnetism.
In 1757 he claimed that he had written to the Royal Society in 1755 about the links between electricity and magnetism, asserting that "there are some things in the power of magnetism very similar to those of electricity" but he did "not by any means think them the same".
In 1760 he similarly claimed that in 1750 he had been the first "to think how the electric fire may be the cause of thunder".
Among the more important of the electrical research and experiments during this period were those of Franz Aepinus, a noted German scholar (1724–1802) and Henry Cavendish of London, England.
Franz Aepinus is credited as the first to conceive of the view of the reciprocal relationship of electricity and magnetism.
In his work "Tentamen Theoria Electricitatis et Magnetism", published in Saint Petersburg in 1759, he gives the following amplification of Franklin's theory, which in some of its features is measurably in accord with present-day views: "The particles of the electric fluid repel each other, attract and are attracted by the particles of all bodies with a force that decreases in proportion as the distance increases; the electric fluid exists in the pores of bodies; it moves unobstructedly through non-electric (conductors), but moves with difficulty in insulators; the manifestations of electricity are due to the unequal distribution of the fluid in a body, or to the approach of bodies unequally charged with the fluid."
Aepinus formulated a corresponding theory of magnetism excepting that, in the case of magnetic phenomena, the fluids only acted on the particles of iron.
He also made numerous electrical experiments apparently showing that, in order to manifest electrical effects, tourmaline must be heated to between 37.5°С and 100°C.
In fact, tourmaline remains unelectrified when its temperature is uniform, but manifests electrical properties when its temperature is rising or falling.
Crystals that manifest electrical properties in this way are termed pyroelectric; along with tourmaline, these include sulphate of quinine and quartz.
Henry Cavendish independently conceived a theory of electricity nearly akin to that of Aepinus.
In 1784, he was perhaps the first to utilize an electric spark to produce an explosion of hydrogen and oxygen in the proper proportions that would create pure water.
Cavendish also discovered the inductive capacity of dielectrics (insulators), and, as early as 1778, measured the specific inductive capacity for beeswax and other substances by comparison with an air condenser.
Around 1784 C. A. Coulomb devised the torsion balance, discovering what is now known as Coulomb's law: the force exerted between two small electrified bodies varies inversely as the square of the distance, not as Aepinus in his theory of electricity had assumed, merely inversely as the distance.
According to the theory advanced by Cavendish, "the particles attract and are attracted inversely as some less power of the distance than the cube.""
A large part of the domain of electricity became virtually annexed by Coulomb's discovery of the law of inverse squares.
Through the experiments of William Watson and others proving that electricity could be transmitted to a distance, the idea of making practical use of this phenomenon began, around 1753, to engross the minds of inquisitive people.
To this end, suggestions as to the employment of electricity in the transmission of intelligence were made.
The first of the methods devised for this purpose was probably that of Georges Lesage in 1774.
This method consisted of 24 wires, insulated from one another and each having had a pith ball connected to its distant end.
Each wire represented a letter of the alphabet.
To send a message, a desired wire was charged momentarily with electricity from an electric machine, whereupon the pith ball connected to that wire would fly out.
Other methods of telegraphing in which frictional electricity was employed were also tried, some of which are described in the history on the telegraph.
The era of galvanic or voltaic electricity represented a revolutionary break from the historical focus on frictional electricity.
Alessandro Volta discovered that chemical reactions could be used to create positively charged anodes and negatively charged cathodes.
When a conductor was attached between these, the difference in the electrical potential (also known as voltage) drove a current between them through the conductor.
The potential difference between two points is measured in units of volts in recognition of Volta's work.
The first mention of voltaic electricity, although not recognized as such at the time, was probably made by Johann Georg Sulzer in 1767, who, upon placing a small disc of zinc under his tongue and a small disc of copper over it, observed a peculiar taste when the respective metals touched at their edges.
Sulzer assumed that when the metals came together they were set into vibration, acting upon the nerves of the tongue to produce the effects noticed.
In 1790, Prof. Luigi Alyisio Galvani of Bologna, while conducting experiments on "animal electricity", noticed the twitching of a frog's legs in the presence of an electric machine.
He observed that a frog's muscle, suspended on an iron balustrade by a copper hook passing through its dorsal column, underwent lively convulsions without any extraneous cause, the electric machine being at this time absent.
To account for this phenomenon, Galvani assumed that electricity of opposite kinds existed in the nerves and muscles of the frog, the muscles and nerves constituting the charged coatings of a Leyden jar.
Galvani published the results of his discoveries, together with his hypothesis, which engrossed the attention of the physicists of that time.
The most prominent of these was Volta, professor of physics at Pavia, who contended that the results observed by Galvani were the result of the two metals, copper and iron, acting as electromotors, and that the muscles of the frog played the part of a conductor, completing the circuit.
This precipitated a long discussion between the adherents of the conflicting views.
One group agreed with Volta that the electric current was the result of an electromotive force of contact at the two metals; the other adopted a modification of Galvani's view and asserted that the current was the result of a chemical affinity between the metals and the acids in the pile.
Michael Faraday wrote in the preface to his "Experimental Researches", relative to the question of whether metallic contact is productive of a part of the electricity of the voltaic pile: "I see no reason as yet to alter the opinion I have given; ... but the point itself is of such great importance that I intend at the first opportunity renewing the inquiry, and, if I can, rendering the proofs either on the one side or the other, undeniable to all.
"Even Faraday himself, however, did not settle the controversy, and while the views of the advocates on both sides of the question have undergone modifications, as subsequent investigations and discoveries demanded, up to 1918 diversity of opinion on these points continued to crop out.
Volta made numerous experiments in support of his theory and ultimately developed the pile or battery, which was the precursor of all subsequent chemical batteries, and possessed the distinguishing merit of being the first means by which a prolonged continuous current of electricity was obtainable.
Volta communicated a description of his pile to the Royal Society of London and shortly thereafter Nicholson and Cavendish (1780) produced the decomposition of water by means of the electric current, using Volta's pile as the source of electromotive force. 
History.16th to 18th century developments.
Understanding of electrical matters began in the sixteenth century.
During this century, the English scientist William Gilbert spent 17 years experimenting with magnetism and, to a lesser extent, electricity.
For his work on magnets, Gilbert became known as the ""Father of Magnetism.""
He discovered various methods for producing and strengthening magnets.
In 1663, the German physicist Otto von Guericke created the first electric generator, which produced static electricity by applying friction in the machine.
The generator was made of a large sulfur ball cast inside a glass globe, mounted on a shaft.
The ball was rotated by means of a crank and a static electric spark was produced when a pad was rubbed against the ball as it rotated.
The globe could be removed and used as source for experiments with electricity.
By the mid—18th century the French chemist Charles François de Cisternay du Fay had discovered two types of static electricity, and that like charges repel each other whilst unlike charges attract.
Du Fay announced that electricity consisted of two fluids: ""vitreous"" (from the Latin for ""glass""), or positive, electricity; and ""resinous,"" or negative, electricity.
This was the "two-fluid theory" of electricity, which was to be opposed by Benjamin Franklin's "one-fluid theory" later in the century.
In 1785, Charles-Augustin de Coulomb developed the law of electrostatic attraction as an outgrowth of his attempt to investigate the law of electrical repulsions as stated by Joseph Priestley in England.
In the late 18th century the Italian physician and anatomist Luigi Galvani marked the birth of electrochemistry by establishing a bridge between chemical reactions and electricity on his essay ""De Viribus Electricitatis in Motu Musculari Commentarius"" (Latin for Commentary on the Effect of Electricity on Muscular Motion) in 1791 where he proposed a ""nerveo-electrical substance"" on biological life forms.
In his essay Galvani concluded that animal tissue contained a here-to-fore neglected innate, vital force, which he termed ""animal electricity,"" which activated nerves and muscles spanned by metal probes.
He believed that this new force was a form of electricity in addition to the ""natural"" form produced by lightning or by the electric eel and torpedo ray as well as the ""artificial"" form produced by friction (i.e., static electricity).
Galvani's scientific colleagues generally accepted his views, but Alessandro Volta rejected the idea of an ""animal electric fluid,"" replying that the frog's legs responded to differences in metal temper, composition, and bulk.
Galvani refuted this by obtaining muscular action with two pieces of the same material.