Experimental researches in electricity (Fourth series). Offprint from Philosophical Transactions. Pres. copy

Faraday, Michael (1791-1867). Experimental researches in electricity (fourth series). 9. On a new law of electric conduction. 10. On conducting power generally. Offprint from Philosophical Transactions (1833). [2], 507-522pp. London: Printed by Richard Taylor, 1833. 280 x 215 mm. Modern wrappers. Vertically creased, occasional spotting, but very good. Presentation Copy, inscribed on the title in Faraday's hand: "St. Georges Med[ical] & Sur[gical] Society from the author." St. George's Hospital library stamps on the title and last page.

First Edition, Offprint Issue. In the section titled "On conducting power generally" Faraday presented the first documented observation of what we now call a semiconductor, i.e., a substance with an electrical conductivity value falling between conductors (such as copper) and insulators (such as glass). Contrary to metals, a semiconductor's electrical conductivity increases with increasing temperature, and its conductivity can be altered by various means. The enormous advances in electronics made in the 20th century would not have been possible without semiconductors.

Faraday's groundbreaking observation appears on page 519:

"I have lately met with an extraordinary case . . . which is in direct contrast with the influence of heat upon metallic bodies . . . The substance presenting this effect is sulphuret of silver [silver sulfide] . . . When a piece of this sulphuret . . . was put between surfaces of platin[um], terminating the poles of a voltaic battery, a galvanometer being also included in the circuit, the needle was slightly deflected, indicating a feeble conducting power . . . On applying a lamp under the sulphuret between the poles, the conducting power rose rapidly with the heat, and at last . . . the sulphuret was found conducting in the manner of a metal."

Jeffreys, Michael Faraday: A List of his Lectures and Published Writings, 215.