Mary D Waller was the daughter of the famous English physiologist, August D. Waller. Dr Waller became Professor of Physics at the Royal Free Hospital Medical School in London. She was fascinated by Chladni’s work and recreated all the forms he discovered, taking his work to a higher level. Her book “Chladni Figures—a Study in Symmetry” 15 was published posthumously in January 1961 and includes details of her novel method of exciting plates employing solid carbon dioxide chips, which she discovered accidentally, as this passage reveals, “In 1932 when it so happened that I was already specially interested in sonic frequencies in connection with some other research work, an itinerant vendor of ice-creams who was selling these to our medical students outside the school, asked me why his bicycle bell gave out a clattering ring when he touched it with Dry-Ice, the material supplied to him to keep his ice-creams frozen. He gave me a lump of solid carbon dioxide with which to experiment and I at once set about investigating this strange new phenomenon.”
She approached the subject of Chladni Figures with scientific rigor and her work represents a rich resource for students of this branch of acoustics, including some of the mathematical equations that describe the phenomena. In the Preface to her book she hints at her discovery of two new general principles concerning symmetries of the vibrations [made visible on metal plates] and she later discusses, in the main body of her book, why these laws have not been recognized before.
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