The beauty and clearness of the dynamical theory, which asserts heat and light to be modes of motion, is at present obscured by two clouds.

— William Thomson, 1st Baron Kelvin, Nineteenth Century Clouds over the Dynamical Theory of Heat and Light (1900)

Source: https://books.google.com/books?id=YvoAAAAAYAAJ&pg=PA363

From his 27 April 1900 Royal Institution lecture.

Topics: physics