- An instrument for studying the motions of sounding systems by optical means. It consists of a tube across whose end is extended a film of soap option thin adequate to offer colored rings, whose type and place are influenced by sonorous vibrations.
- a guitar for studying the movements of sounding figures by optical means. It is made from a tube throughout the end which is stretched a film of detergent answer thin adequate to provide colored bands, the proper execution and position of which are affected by sonorous oscillations.
- An instrument for observing the color-figures of fluid movies underneath the activity of sonorous oscillations.