Benjamin Franklin's glass armonica spins its glass bowls — ChillScroll

Nested glass bowls mounted on a spindle inside a dark wooden armonica

Benjamin Franklin's glass armonica spins its glass bowls

Franklin's instrument places glass bowls of different sizes inside one another on a rod. A foot pedal turns them, and touching their rims with damp fingers makes different notes.

It is a row of singing glasses that agreed to share one axle.

Source · The Franklin Institute ↗