Case containing a set of six metal buttons with various types of diffraction patterns engraved on their top surface. Made by John Barton, these samples were drawn using his own ruling engine to inscribe hundreds of parallel lines on each button. The decoration produces a rainbow of colours due to the interference of light when it strikes the closely ruled lines. Ornamented pieces with diffraction patterns ruled upon them became popular with the public during the 19th century.
© Science Museum / Science & Society Picture Library