The Old Observatory of Tartu Observatory — Completed in 1810. Friedrich Georg Wilhelm von Struve worked here. Photo Credit: By BigFlyingSaucer - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=20206740
Diagram of Faraday's iron ring apparatus — The changing magnetic flux of the left coil induces a current in the right coil Photo Credit: By Eviatar Bach - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=16608674