While living in England as a Pennsylvanian diplomat in the 1750s, Franklin stopped by Cambridge University to take in a concert by Edmund Delaval, a professional wine glass player. Delaval arranged a collection of wine glasses on a table, "tuned" them by filling each with a different quantity of water and then played them by carefully rubbing their rims in succession. As the audience soaked up the smooth, ethereal sound of the glasses, Franklin couldn't help but notice room for improvement.
Playing wine glasses is woefully time-consuming to set up -- and hard on the wrists to play. Franklin wracked his brain to figure out he could create music from glass without needing to empty out his kitchen cupboards. Two years of experimentation later, Franklin debuted his glass armonica, a collection of different-sized glass bowls arranged on a rotating shaft. By spinning the shaft with a foot pedal and running wetted fingers over the rotating bowls, Franklin found he could coax out chords and melodies that Delaval could only dream of.
The new instrument was soon making the rounds of parlors and concert halls across Europe and America. Mozart and Beethoven penned music for the new instrument, and Franz Mesmer, a pioneer in hypnosis, used the instrument to guide his patients into deeper trances. In the 19th century, however, the popularity of the instrument died out as a rumour spread that the ghostly sounds it produced could provoke insanity in the listener.