Ernst Chladni at the understanding of electron orbitals. Since at least 1738, a musical instrument called a "Glasspiel" or "verrillon", created by filling beer glasses with varying amounts of water, was popular in Europe. The beer glasses were struck by wooden mallets shaped like spoons to produce "church and other solemn music". Benjamin Franklin was sufficiently impressed by a verrillon performance on a visit to London in 1757 that he created his own instrument, the glass armonica, in 1762. Franklin's armonica inspired several other instruments, including two created by Chladni. In 1791, Chladni invented the musical instrument called the "euphon" (not to
Glass harmonica produce a clear tone. Some attempted improvements on the armonica included adding keyboards, placing pads between the bowls to reduce sympathetic vibrations, and using violin bows. Another supposed improvement claimed in ill-informed post-period observations of non-playing instruments was to have the glasses rotate into a trough of water. However, William Zeitler put this idea to the test by rotating an armonica cup into a basin of water; the water has the same effect as putting water in a wine glass – it changes the pitch. With several dozen glasses, each a different diameter and thus rotating with a different depth,