As the popularity of playing musical glasses increased during the mid-18th century, Benjamin Franklin, American statesman and inventor, designed a more utilitarian version of the fashionable instrument--the armonica. He had a glassblower make him a set of 36 hemispherical bowls, graduated in size, with a hole in the middle so that they could be placed in a row on a horizontal iron spindle and rotated by a treadle mechanism like that of old-fashioned sewing machines. The Museum's example is equipped with a crank rather than a treadle, to rotate the spindle. The player touches the glass rims with moistened fingers to create the instrument's distinctively ethereal, ringing sound.