Abstract: Rntgen′s fame today rests solely on his discovery of X-rays and takes no account of his great contribution to electromagnetic theory. The experiment proving the existence of the “displacement current”done by Rntgen is described in his paper, which was recognized as the most important experiment of the 19th century. It was so famous at that time, yet today has been all but completely forgotten. Our aim is to give you a comprehensive understanding of Rntgen himself and the significance of his achievement for the construction of the edifice of 19th century physics.