Paper, 'On a peculiar class of acoustical figures - and on certain forms assumed by groups of particles upon vibrating elastic surfaces' by M [Michael] Faraday Appendix to this paper found at PT/19/4. Subject: Physics Published in volume 121 of Philosophical Transactions as 'On a peculiar class of acoustical figures; and on certain forms assumed by groups of particles upon vibrating elastic surfaces'. Written by Faraday at the Royal Institution. Received by the Royal Society on 7 April 1831. Read 12 May 1831. Abstract published in Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London [later Proceedings of the Royal Society of London], Volume 3, 1837. 21 March 1831