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Arrow1700 - 1749

Timelines

Sir Isaac Newton of England, remembered as one of history’s greatest scientists and mathematicians, published his famous treatise on light and optics early in the century. Among other issues, it addressed a debate begun years earlier over whether light was a particle or a wave. In opposition to previous theories, Newton determined it was made up of particles, or “corpuscles.” Scientists continued to go back and forth on the issues for centuries, eventually recognizing light as electromagnetic waves and later agreeing, thanks to another brilliant scientist, Albert Einstein, that light was both a particle and a wave.

Hauksbee electrostatic generator

A compatriot of Newton, Francis Hauksbee, was employed by the Royal Society, an independent scientific academy established in London in 1662. Though relatively unschooled, Hauksbee possessed a gift for science, in particular the design and construction of experimental equipment. In the early 1700s he set to work to understand barometric light, or the glow that appears in a barometer after it is shaken, a phenomenon poorly understood at the time.

Hauksbee came to realize the glow was electric – the result of the friction of the mercury moving in the barometric tube. He went on to investigate whether other materials would bring about such an effect, and for this work constructed an electrostatic generator that improved greatly on Otto von Guericke’s 1660 design. With it he produced light in a glass tube bright enough, he reported, to read by – a crude precursor to the light bulb. He also created the first visualization of electric lines of force with the generator, attaching threads to it that indicated the presence of the invisible lines, though Hauksbee did not comprehend the meaning of what he saw. Hauksbee also misunderstood another phenomenon observed in his experiments: that by simply bringing a glass globe near another electrified globe, he could electrify the first (what’s known as electrification by influence).

Another Englishman, Stephen Gray, followed Hauksbee’s work in the field with important contributions of his own, the greatest of which was his discovery of conduction. Using a variety of materials over many years, Gray transmitted electricity over ever greater distances. He eventually moved his experiments out of doors and built lines hundreds of feet in length. He came to realize that some materials conduct electricity well (what we know as conductors), while others don’t (insulators).

A few years later, across the English Channel, French chemist Charles-François de Cisternay du Fay repeated and expounded on the experiments of Gray, von Guericke and others, coming to a fuller understanding of the force of repulsion. In so doing he gained some critical insights, including that most things could be electrified just by rubbing them, and that materials conduct better when wet.

But du Fay’s most significant discovery was the existence of two types of electricity. He deduced this with the following experiment. First, the chemist brought a gold leaf into contact with a rubbed glass globe, which as expected attracted, then immediately repelled, the gold leaf. He then put the gold leaf near a different rubbed object – this time a piece of amber-like copal, and was astonished to see the gold leaf attracted to the copal. He had expected the two electrified objects to repel each other. Du Fay determined there must be two types of electricity, and labeled one vitreous and the other resinous. Some materials produced the first type, while others generated the second. Though Du Fay astutely observed the opposing behaviors, he was incorrect, of course, in his accounting of them. Benjamin Franklin would set the record straight a few years down the line.

Toward the middle of the century, a simple kind of capacitor was devised that became a very important – and entertaining – experimental tool. Invented independently by German cleric E. Georg von Kleist and Dutch physicist Pieter van Musschenbroek of the University of Leiden, it came to be known as the Leyden jar. It consisted of a water-filled glass jar, coated inside and out with metal foil and topped by a stopper through which a wire ran. The other end of this wire could be connected to an electrostatic generator, so that the electricity it made would flow into and be stored in the jar. Though dangerous if used without care (van Musschenbroek nearly electrocuted himself with it), the jar was employed by many prominent scientists in their investigations of electricity (including Benjamin Franklin) and gave rise to bizarre demonstrations of electric current that featured long chains of human guinea pigs.

1700 - 1749

1706

English physicist Sir Isaac Newton publishes Opticks, his collection of papers relating to light, color and optics. In it he outlines his corpuscular theory of light that holds that light is made up of particles, not waves, as other scientists had suggested.

1706

Francis Hauksbee of London invents an electrostatic generator composed of a glass sphere turned by a crank that produces an electric charge through fiction, which a metal chain is then utilized to capture, a significant improvement over the more primitive version produced by Otto von Guericke several decades earlier.

1708

English scientist William Wall notes a similarity between thunder and lightning and the cracking sounds and sparks produced by electrified objects and his observation are published in Philosophical Transactions.

1709

Physico-Mechanical Experiments on Various Subjects. Containing an Account of Several Surprizing Phenomena Touching Light and Electricity is published by Francis Hauksbee and becomes an important early work in the areas of electricity and electroluminescence.

1716

English mathematician and astronomer Edmond Halley correctly speculates that the atmospheric phenomenon of aurorae is related to the effects of the magnetic field of the Earth.

1722

Through close observation of the needle of a compass, London instrument maker George Graham discovers the diurnal variation of magnetic declination.

1729

Chemist Stephen Gray of London demonstrates the conductivity of electricity and determines that it is the surface of an object that holds its charge.

1733

French chemist Charles-François de Cisternay du Fay speculates that there are two different types of electricity, which he refers to as resinous (-) and vitreous (+), notes the repulsion of like charges and the attraction of unlike charges, and determines that string is more conductive when wet.

1742

Thomas Le Sueur and Francis Jacquier publish an edition of Isaac Newton’s Principia and include a note to the text that demonstrates an inverse-cube law of the force between two magnets.

1745

The Leyden jar, the first practical device for storing electric charge, is invented independently by German cleric E. Georg von Kleist and Dutch physicist Pieter van Musschenbroek.

1745

Jean-Antoine Nollet, a French clergyman and physicist, theorizes that electrical matter continuously flows between two charged objects.

1745

English physicist Gowin Knight develops a method of producing artificial magnets that retain their magnetization for extended periods of time. The new magnets are used in the Knight compass, which becomes very popular among mariners and scientists.

1746

In a demonstration of electricity for King Louis XV, Jean-Antoine Nollet discharges a Leyden jar so that the current passes through a line of 180 Royal Guards. He would later carry out a similar feat involving a chain of Carthusian monks that extended more than a kilometer.

1746

British scientist William Watson develops the concept of the conservation of electrical charge, in which there exists a single electrical fluid that is not created or destroyed, but only transferred from one object to another. Soon after, Benjamin Franklin more fully develops the theory of conservation.

1746

Johann Heinrich Winckler, a professor at the University of Leipzig, endeavors to utilize electricity to communicate telegraphically across long distances.

1747

English physicist and chemist Henry Cavendish begins measuring the conductivity of various substances by comparing the shocks he receives when he discharges Leyden jars through them.

1748

William Watson, Henry Cavendish and other colleagues attempt to measure the velocity of electricity as it traveled through a circuit more than 12,000 feet long and mistakenly conclude that it is instantaneous.

1748

Jean-Antoine Nollet builds an early electroscope, an electrometer comprised of a suspended pith ball that moves in response to the electrostatic attraction and repulsion of a charged body.



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