In 1884, Thomson led a master class on "Molecular Dynamics and the Wave Theory of Light" at Johns Hopkins University.Kargon, Robert and Achinstein, Peter (1987) Kelvin's Baltimore Lectures and Modern Theoretical Physics: historical and philosophical perspectives. MIT Press. Kelvin referred to the acoustic wave equation describing sound as waves of pressure in air and attempted to describe also an electromagnetic wave equation, presuming a luminiferous aether susceptible to vibration. The study group included Michelson and Morley who subsequently performed the Michelson–Morley experiment, which subsequently found no luminiferous aether. Thomson did not provide a text but A. S. Hathaway took notes and duplicated them with a Papyrograph. As the subject matter was under active development, Thomson amended that text and in 1904 it was typeset and published. Thomson's attempts to provide mechanical models ultimately failed in the electromagnetic regime. Starting from his lecture in 1884, Kelvin was also the first scientist to formulate the hypothetical concept of dark matter; he then attempted to define and locate some "dark bodies" in the Milky Way.
