Below is Mary Henry’s picture of her father’s (Joseph Henry) galvanometer. The caption at the top reads: “Galvanometer made by Henry while in Albany and the one probably used in the great discovery of magneto-electricity.” By magneto-electricity, she means electricity produced by magnetism, or induction. This is a discovery generally credited to Faraday, but Henry made the same discovery independently at the same time. Faraday, however, managed to publish the results first.


Click on different parts of the picture to explore the components of a galvanometer.

This is a picture of the same galvanometer, taken in July 2010. Click on the picture below for an video of the galvanometer in action.

Henry Quantity (high current) Galvanometer

In comparison with the galvanometer above, this is a picture of Henry’s intensity galvanometer, which he made in 1840 (“The Rise of the Electrical Industry during the Nineteenth Century,” by Malcolm MacLaren). For an explanation of the difference between the two, click on the picture to the right.

Click here to look at the history and development of the galvanometer.

Click here to look at theories to explain the galvanometer.