Some of the work of Professor AO Rankine, first presented to the Physical Society of London in 1919 is reviewed. Prior to discussing his work, elements of acousto-optics, and developments to that time are sketched in order to provide a content for Rankine's innovations. His initial proposal was for a system to transmit speech sounds over distances of several kilometers using light waves. Various possibilities were discussed, the most successful of which was based on the interference of a vertical grid with a superimposed image of itself. This proposal was shortly followed by a successful demonstration of the possibility of using this 'photophone' in conjunction with a rapidly moving photographic film to record any type of sounds. They could then be replayed using a relatively simple optical system and a selenium detector. Some comments are made on the ration between Rankine's system and more recent developments in optical sound recording.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.