Lord Rayleigh served as President of Royal Society from 1905 to 1908, when he became Chancellor of the University of Cambridge. In 1904 he was awarded a Nobel Prize. He received the physics award while Ramsey, with whom he had conducted the research and anunced the discovery of argon, received the Nobel Prize for chemistry. In 1906 he published his electron fluid model of the atom, a modification of Thomson's 'plum pudding' proposal. This was superseded by a series of other (also invalid) models, until Bohr's atomic theory of 1913. In 1907 Rayleigh published a detailed observational study on how humans can perceive sound and distinguish the directions of pure and complex tones. His interest in optics also continued, with a 1907 analysis of the theoretical basis for unusual banding patterns arising when polarised light was shone on diffraction gratings. This volume includes his papers from 1902 to 1910.