Galvanic phenomena were described in the literature before it was understood that they were of an electrical nature. In 1752, when the Swiss mathematician and physicist Johann Georg Sulzer placed his tongue between a piece of lead and a piece of silver, joined at their edges, he perceived a taste similar to that of iron(II) sulfate. Neither of the metals alone produced this taste. He realized that the contact between the metals probably did not produce a solution of either on the tongue. He did, however, not realize that this was an electrical phenomenon. He concluded that the contact between the metals caused their particles to vibrate, producing this taste by stimulating the nerves of the tongue.