In extending the electrical experiments of Stephen Gray, Charles-François de Cisternay Du Fay discovered two types of electric charge, which he called vitreous and resinous electricity. He demonstrated that like charges repel and unlike charges attract, the two-fluid theory of electricity. Benjamin Franklin modified this idea with his one-fluid theory, in which an excess or deficiency of the electric fluid was designated positive or negative.

The Greek natural philosopher Thales discovered the attractive effect of rubbed amber, Amber effect (electricity)
Science;electricity as a result of which the Greek term elektron (amber) became associated with the phenomenon and eventually developed into the term “electricity.” English physician William Gilbert Gilbert, William began the modern study of electrical phenomena in the late sixteenth century when he demonstrated that about thirty materials could be electrified. During the seventeenth century, the study of electrical phenomena was often considered practice in the occult and so was often neglected. Electrical studies received impetus when the English pensioner and electrical experimenter Stephen Gray discovered the conduction of “electric virtue” in 1729 and found a distinction between conductors and insulators. This led directly to the work of the French scientist Charles-François de Cisternay Du Fay and his two-fluid theory of electricity, Electricity;two-fluid theory of[two fluid theory] in which like fluids repel and unlike fluids attract. Du Fay’s work led to the experiments of Benjamin Franklin and his one-fluid theory of Electricity;one-fluid theory of[one fluid theory] positive and negative electricity. [kw]Du Fay Discovers Two Kinds of Electric Charge (1733)
[kw]Charge, Du Fay Discovers Two Kinds of Electric (1733)
[kw]Electric Charge, Du Fay Discovers Two Kinds of (1733)
[kw]Kinds of Electric Charge, Du Fay Discovers Two (1733)
[kw]Discovers Two Kinds of Electric Charge, Du Fay (1733)
Electrical charges
[g]France;1733: Du Fay Discovers Two Kinds of Electric Charge[0810]
[c]Science and technology;1733: Du Fay Discovers Two Kinds of Electric Charge[0810]
[c]Physics;1733: Du Fay Discovers Two Kinds of Electric Charge[0810]
Du Fay, Charles-François de Cisternay
Hauksbee, Francis
Gray, Stephen
Franklin, Benjamin
[p]Franklin, Benjamin;electricity

Francis Hauksbee, an uneducated instrument maker and demonstrator at the Royal Society of London, revived interest in electricity in eighteenth century England. Encouraged by Sir Isaac Newton, who was serving as the new president of the society, Hauksbee enhanced his electrical experiments in 1705 by using a long glass tube in place of amber, observing electrostatic repulsion. When he rubbed a glass tube, the tube acquired the characteristic of attracting some kinds of matter and repelling other kinds of matter.

Gray, a dyer by trade, followed up on these electrical experiments. In 1708 he transmitted to the Royal Society Royal Society, England the results of his experiments with a glass tube, which were similarly performed by Hauksbee. Gray’s first paper, which appeared in the society’s Philosophical Transactions in 1720, described light and sparks from a glass tube when rubbed in the dark and identified several new materials that could be electrified. A second paper in 1729 described his discovery of electrical conduction. Electrical conductivity After placing corks in the ends of a glass tube to keep out dust, he found that the cork attracted and repelled a down feather. He concluded that there was an attractive “virtue” communicated to the cork by the “excited” tube.

In his 1729 paper, Gray described a series of experiments on the conduction of electric virtue. He inserted a rod into one of the corks and observed attraction to an ivory ball on the other end of the rod. He then found that metal wire from the cork in the glass tube would conduct electricity to the ivory ball. Working with friends, he was able to observe attraction by the ivory ball suspended on 34 feet of packthread from the glass tube. He then made several attempts to pass the electric virtue along a horizontal line suspended by packthread from a roof beam, but his lack of success led him to conclude that the electricity escaped through the beam (grounding). He finally succeeded by using silk thread to support his horizontal line.

Gray continued his experiments in a barn, succeeding with a packthread line up to 293 feet; when he used metal wire to support a longer line, however, the experiment failed. Using silk supports again, he succeeded in transmitting electricity up to about 650 feet. Thus, he finally recognized the basic distinction between insulators such as silk and glass and conductors such as metals and packthread. In a 1732 paper, he reported on the electrification of materials by the influence of an electrified glass tube without direct contact.

Electrical studies were soon begun in Paris at the French Academy of Sciences Academy of Sciences, France by Du Fay, a self-trained scientist who published papers in all the sciences recognized by the academy and became superintendent of the Royal Gardens. In 1732, Du Fay heard of Gray’s experiments and reviewed the existing literature in his first memoir on electricity for the academy. In half a dozen other memoirs on electricity, Du Fay reported his experiments and discoveries. He showed that all materials could be electrified: solids by friction if properly dried and liquids by electrical influence. He repeated Gray’s experiments on conduction, obtaining better results by using wet packthread supported on glass tubes up to a distance of 1,256 feet.

In 1733, Du Fay found that gold foils could be attracted to an electrified glass tube, but they would repel each other when approached or touched by the tube. This appears to be the first clear demonstration of electric repulsion. However, to his surprise, when a rod of gum resin electrified one of the gold foils, it attracted the other gold foil. This led him to recognize the existence of two kinds of electricity and to determine how they behave.

Du Fay’s experiments led him to distinguish “vitreous” electricity, Vitreous electricity conducted by hard materials such as glass, rock crystal, and precious stones, and “resinous” electricity, Resinous electricity conducted by softer materials such as amber, gum resin, and paper. He then described how electrified vitreous objects attract resinous objects, but how two vitreous objects or two resinous objects repel each other. Although Du Fay never referred to “fluids,” his discovery was called the two-fluid theory of electricity, that bodies with like “electric fluids” repel and those of unlike fluids attract. Du Fay sent his results to the Royal Society, where they were translated into English and published in the Philosophical Transactions for 1734. Transferring electric fluid to an object came to be viewed as loading or charging the object, leading to the term “electric charge.” Electrical charges

At Boston in 1746, Benjamin Franklin was introduced to electrostatic phenomena and began to experiment with them. In 1747 he stated his one-fluid theory of electricity, in which transferring electricity causes one object to lose electric charge, becoming negative, and the other object to gain charge, becoming positive. Later he identified positive and negative charge with Du Fay’s vitreous and resinous fluids, respectively, which Franklin viewed as a surplus or deficiency of a single electric fluid. Franklin’s assumption that electrification does not create or destroy charge, but only transfers it from one body to another, implies the law of conservation of electric charge.

The identification of positive and negative electric charges and their properties led to the modern science of electricity. By using the mathematical terms “plus” and “minus,” Benjamin Franklin suggested the possibility that electricity is quantitative and measurable. Franklin’s theory led to development of the law of electric force by French engineer Charles Coulomb Coulomb, Charles in 1785. The discovery of ways to maintain the flow of electric charge as an electric current opened up the field of practical electricity for heating, lighting, telegraphy, and many other applications in the nineteenth century.

Ironically, Franklin’s choice of positive and negative charges turned out to be mistaken. The discovery of the electron Electrons by the English physicist J. J. Thomson at the end of the nineteenth century made it evident that vitreous materials tend to lose electrons and thus should have been called negative, while resinous materials gain electrons and should have been called positive. Electrons were therefore designated as negative and are the basic unit of negative charge. The corresponding positive unit of charge, the proton, was discovered early in the twentieth century with an equal and opposite charge, but the proton was found to have a mass nearly two thousand times larger than that of the electron.

The atomic number of an element corresponds to the number of protons in the atomic nucleus, with an equal number of electrons surrounding the nucleus. Electric current in most conductors consists of the flow of only electrons, reflecting Franklin’s one-fluid theory, but both electrons and protons flow in gaseous discharges, matching Du Fay’s two-fluid theory. The existence of both electrons and protons seems to favor Du Fay’s theory.

• Bodanis, David. Electric Universe: The Shocking True Story of Electricity. New York: Crown, 2005. A fascinating exploration of the history of electricity that looks at inventions from the light bulb to the computer. Includes a helpful annotated bibliography.
• Fara, Patricia. An Entertainment for Angels: Electricity in the Enlightenment. New York: Columbia University Press, 2002. Fara examines early electrical experiments. Includes bibliographical references.
• Heilbron, J. L. Elements of Early Modern Physics. Berkeley: University of California Press, 1982. The third of three chapters, “The Case of Electricity,” describes eighteenth century developments, with many illustrations.
• Roller, Duane, and Duane H. D. Roller. The Development of the Concept of Electric Charge: Electricity from the Greeks to Coulomb. Cambridge, Mass.: Harvard University Press, 1954. This classic study of early electrical studies includes extensive quotations from original sources.
• Schiffer, Michael Brian. Draw the Lightning Down: Benjamin Franklin and Electrical Technology in the Age of Enlightenment. Berkeley: University of California Press, 2003. The first two chapters describe the electrical researches that led to Franklin’s work.
• Schlagel, Richard H. From Myth to Modern Mind: A Study of the Origins and Growth of Scientific Thought. New York: Peter Lang, 1996. Chapter 8, “The Newtonian Legacy,” includes a good discussion of early electrical research.

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