 A little later he studied the absorption spectrum of the atmosphere, and found that the Fraunhofer lines varied according to the time of day, and that the change must be due to some constituents of the earth's atmosphere.In this research he was joined by Sir David Brewster, and together they produced a paper on the lines of the solar spectrum in 1860.The most important work of Gladstone in this direction was the long series of observations on the refraction and dispersion of liquids, which originated with a study of the "Influence of Temperature on the Refraction of Light," (Phil.