How to Send a Secret Message from Rome to Paris in the Early Modern Period: Telegraphy between Magnetism, Sympathy, and Charlatanry

In 1558, the famous natural magician Giambattista della Porta was the first to allude to a method of transmitting secret messages by using manipulated magnetic compasses. Soon thereafter, this idea, known in modern historiography as ‘magnetic telegraphy’, was spelled out and advertised by many early modern scholars as a promising technology of communication by action at a distance. In 1609, Daniel Schwenter created the most sophisticated design for the fulfillment of this potential: two compass needles were to be magnetized in a highly codified procedure to establish a sympathetic bond between them. Used in a compass circumscribed by an alphabet, one needle would turn to a certain letter whenever the other needle was moved to that same letter. Through ‘sympathy’, it was thought that this could made to occur even over a distance of many miles. The idea’s first critic, the Jesuit, Leonardo Garzoni, was quick to dismiss it as charlatanry, and many later authors argued that the device could not work as there was no such ‘sympathy’ or magnetism between the two devices. Though only a fanciful pipe dream of natural magic, this pseudo-technology of a magnetic telegraph yet testifies to the imagination of early modern scholars in having prefigured the modern reality of instantaneous global communication.