One of these courses of six lectures given to the Society of Apothecaries of London in 1868 was subsequently published, with additions, in an admirably illustrated volume which had a considerable measure of success—a second edition, still more largely augmented owing to the extraordinary rapidity with which knowledge on celestial chemistry increased, being called for within a year. In the preparation of a third and fourth edition he was assisted by his friend Dr. Schuster. As the successive editions show, the rate at which literature accumulated round the subject was altogether unprecedented in the history of scientific discovery. Roscoe made an attempt to apply the spectroscope to the Bessemer process of steel manufacture, and for this purpose caused a long series of observations to be made, first at Brown’s Atlas works in Sheffield, and then at the Crewe works of the L. & N.W. Railway Company, when a considerable amount of information concerning the peculiarities of the spectrum of the converter-flame was gained, mainly by the observations of Dr. W. Marshall Watts, a former student and one of his assistants, who took over the subsequent conduct of the inquiry. Considering his interest in the subject, comparatively little original work on spectroscopy was published by Roscoe. The following is a list of the inquiries with which he was concerned: “On the Effect of Increased Temperature upon the Nature of the Light Emitted by the Vapour of Certain Metals on Metallic Compounds.” By H. E. Roscoe and R. B. Clifton. _Manchester Phil. Soc. Proc._ II. (1860-1862), pp. 227-230. “Note on the Absorption-spectra of Potassium and Sodium at Low Temperatures.” By H. E. Roscoe and A. Schuster. _Roy. Soc. Proc._ XXII. (1874), pp. 362-364. “On the Absorption-spectra of Bromine and Iodine Monochloride.” By H. E. Roscoe and T. E. Thorpe. _Phil. Trans._ CLXVII. (1878), pp. 207-212. “Note on the Identity of the Spectra Obtained from the Different Allotropic Forms of Carbon.” By H. E. Roscoe and A. Schuster. _Manchester Lit. Phil. Soc. Proc._ XIX. (1880), pp. 46-49. “The Spectrum of Terbium.” By H. E. Roscoe and A. Schuster. _Chem. Soc. Jour._ XLI. (1882), pp. 283-287. The only attempt he was able to make to contribute to our knowledge of the chemistry of the sun by spectroscopic observations had an unlucky ending. He formed one of the members of the Government expedition sent to Sicily to observe the total solar eclipse of December 22, 1870. The following letters refer to this subject: VICTORIA PARK, MANCHESTER, _November 2, 1870_.