1850-1869

French physician Guillaume Benjamin Armand Duchenne publishes information on his long-running study on facial muscles and their expression of emotion, discoveries made from applying electrical stimulus directly to or through the skin.

Edward Sabine, an English astronomer, discovers a correlation between the sunspot cycle and magnetic activity on Earth.

German physicist Hermann von Helmholtz's work with electricity and muscle tissue leads him to publish "Some laws concerning the distribution of electric currents in conductors with applications to experiments on animal electricity." This work includes a mathematical demonstration of what is now known as Thévenin's theorem of electric circuits.

Scottish physicist James Clerk Maxwell writes his first essay related to electricity, On Faraday's Lines of Force, in which he relates Faraday's conception of lines of force to the flow of a liquid and uses analytical mathematics to derive equations for electric and magnetic phenomena.

Physicist Gustav Kirchhoff expands on the work of compatriots Weber and Kohlrausch, demonstrating that electromagnetic signals can be transmitted on a highly conductive wire at the speed of light.

A transatlantic electric telegraph cable is successfully laid across the ocean floor, despite an earlier failed attempt. After just six weeks, the newly installed line stops working.

French physicist Gaston Planté builds the first rechargeable battery from two lead sheets rolled into a cylinder, submerged in a diluted sulfuric acid solution, and then charged.

The first transcontinental telegraph line is completed in America.

The Committee on Electrical Standards of the British Association for the Advancement of Science completes a report defining units of electromotive force and resistance based on millimeters, grams and seconds (mgs system). Less than 10 years later the group would recommend switching to a centimeter, gram and second (cgs) system.

French engineer Georges Leclanché invents the dry cell battery that bears his name and continues to be widely used, albeit in a somewhat modified form, today.

Zénobe-Théophile Gramme, an electrical engineer born in Belgium, invents a practical continuous-current electrical generator known as the Gramme dynamo, which a few years later is discovered by accident to be reversible so that it can also be utilized as an electric motor.