Stephen Gray

Stephen Gray (December 1666, Canterbury; February 7, 1736, London) was an English physicist and natural scientist, best known for his contributions to the field of electrical conductivity.

Biography and work

Gray was initially dedicated to astronomy (approximately from 1690), an area of knowledge in which he made some contributions to the measurement of solar and lunar eclipses, also devoting himself to the astronomical observation of sunspots and the study of Jupiter's satellites.

Experiment by Stephen Gray and Granville Wheler in 1730

From 1702 he reoriented his work as a researcher towards electricity and later, more precisely, towards the subject of electrical conductivity. His most notable contribution (published in 1729) is the finding that electricity can be conducted through of a conducting body. This discovery is often described as "one of the most important of the 18th century in the area of electricity", would have been a relatively serendipitous product, while he was experimenting with the attractive properties of static electricity, which he originally studied.

Later, he established a first classification of bodies with respect to their electrical conductivity, listing the conductive materials and the non-conductive or "insulating" materials, a work he carried out together with the researchers G. Wheler and J. Godfrey.

His research in the field of electricity earned him the first two awards of the Copley Medal by the Royal Society in two successive years (in 1731 and in 1732).

In his experiments he also discovered that for electricity to flow through the conductor, it had to be isolated from ground.

Despite his extensive contributions, very little exact biographical information is known about Gray. A possible explanation for this enigmatic situation has been provided by Robert A. Chipman, who suggests that Stephen Gray had been friends with a person who in turn was not liked by Newton. For this reason, Gray would have fallen out of favor with Newton in circumstances that the latter had taken office as president of the Royal Society and would have been marginalized from the scientific world. His reinstatement and rehabilitation, according to this author, would only have been possible after Newton's death.

Reception and subsequent influence

Gray's work served as a basis for Charles François de Cisternay du Fay to distinguish in 1733 two «forms» or «types of electricity» (today it is said two different forms of electric charge) in accordance with his observations of electrification by rubbing: the "vitreous electricity" produced by rubbing glass and the "resinous electricity" produced by rubbing objects made of that material. Dufay observed that two bodies that were charged with the same "type of electricity" repel each other, while two bodies that were charged with different types were attracted to each other.

Published work

• Part of a Letter from Mr Gray, concerning an Unusual Parhelion and Halo. In: Philosophical Transactions. Vol. 22, 1700, p. 535, doi 10.1098/rstl.1700.0021.
• Part of a Letter from Mr Stephen Gray to the Publisher, containing His Observations on the Fossils of Reculver Clisfe, and a New Way of Drawing the Meridian Line, With a Note on This Letter by the Publisher. In: Philosophical Transactions. Vol. 22, 1700, pp. 762–764, doi 10.1098/rstl.1700.0068.
• A Letter from Mr Stephen Gray, concerning Drawing the Meridian Line by the Pole Star, and Finding the Hour by the Same. In: Philosophical Transactions. Vol. 22, 1700, pp. 815–819, doi 10.1098/rstl.1700.0079.
• Part of Two Letters from Mr Stephen Gray, concerning the Spots of the Sun, observ'd by Him in June Last. In: Philosophical Transactions. Vol. 23, 1702, pp. 1502–1504, doi 10.1098/rstl.1702.0066.
• An Account of Some New Electrical Experimentp.. By Mr. Stephen Gray. In: Philosophical Transactions. Vol. 31, 1720, pp. 104-107, doi 10.1098/rstl.1720.0025.
• A Letter to Cromwell Mortimer, M. D. Secr. R. S. Containing Several Experiments concerning Electricity; By Mr. Stephen Gray. In: Philosophical Transactions. Vol. 37, 1731, p. 18–44, doi 10.1098/rstl.1731,0005.
• A Letter concerning the Electricity of Water, from Mr. Stephen Gray to Cromwell Mortimer, M. D. Secr. R. p... In: Philosophical Transactions. Vol. 37, 1731, pp. 227–260, doi 10.1098/rstl.1731.0040.
• A Letter from Mr. Stephen Gray to Dr. Mortimer, Secr. R. p.. Containing a Farther Account of His Experiments concerning Electricity. In: Philosophical Transactions. Vol. 37, 1731, p. 285–291, doi 10.1098/rstl.1731.0050.
• Two Letters from Mr. Stephen Gray, F. R. S. to C. Mortimer, M. D. Secr. R. p.. Containing Farther Accounts of His Experiments concerning Electricity. In: Philosophical Transactions. Vol. 37, 1731, pp. 397–407, doi 10.1098/rstl.1731.0067.
• A Letter from Mr. Stephen Gray, F. R. S. to the Publisher, Containing an Account of the Same Eclipse of the Sun, as Observed by Himself at Norton-Court: And at Otterden-Place, by Granville Wheler Esq; F. R. S. Both in Kent. In: Philosophical Transactions. Vol. 38, 1733, pp. 114–116, doi 10.1098/rstl.1733.0021.
• Experiments and Observations upon the Light That is Produced by Communicating Electrical Attraction to Animal or Inanimate Bodies, Together with Some of Its Most Surprising Effects; Communicated in a Letter from Mr. Stephen Gray, F. R. S. to Cromwell Mortimer, M. D. R. S. Secr. In: Philosophical Transactions. Vol. 39, 1735, p. 16–24, doi 10.1098/rstl.1735,0006.
• A Letter from Stephen Gray, F. R. S. to Dr. Mortimer, Secr. R. p.. Containing Some Experiments Relating to Electricity. In: Philosophical Transactions. Vol. 39, 1735, p. 166-170, doi 10.1098/rstl.1735.0028.
• Mr. Stephen Gray, F. R. S. His Last Letter to Granville Wheler, Esq; F. R. S. concerning the Revolutions Which Small Pendulous Bodies Will, by Electricity, Make Round Larger Ones from West to East as the Planets do Round the Sun. In: Philosophical Transactions. Vol. 39, 1735, pp. 220, doi 10.1098/rstl.1735.0044.
• An Account of Some Electrical Experiments Intended to be Communicated to the Royal Society by Mr. Stephen Gray, F. R. p. Taken from His Mouth by Cromwell Mortimer, M. D. R. S. Secr. on Feb. 14, 1735-6. Being the Day before He Died. In: Philosophical Transactions. Vol. 39, 1735, pp. 400–403, doi 10.1098/rstl.1735.0082.