Carl Friedrich Gauss (1777 – 1855), director of Gottingen Observatory, and his colleague Wilhelm Weber (1804 – 1891) invented one of the first telegraphs and used it to communicate with each other.
In order to coordinate their study of geomagnetism, the two men strung a three-kilometer-long wire from Weber's physics lab to Gauss's observatory. It was the first practical use of a telegraph anywhere in the world. They were unable to get financial backing from the observatory for their invention, however, and it languished.
Gauss went on to later develop a method (still in use today) for quantifying the strength of a magnetic field. He also made significant contributions to our understanding of the Earth's magnetic field.