Herschel returned to his English home in the spring of 1838. As was natural and right, he was welcomed with an enthusiastic greeting. By the queen at her coronation he was created a baronet; and, what to him was better than all such rewards, other men caught the contagion of his example, and laboured in fields similar to his own, with an adequate portion of his success. Herschel was a highly accomplished chemist. His discovery in 1819 of the solvent power of hyposulphite of soda on the otherwise insoluble salts of silver was the prelude to its use as a fixing agent in photography; and he invented in 1839, independently of Fox Talbot, the process of photography on sensitized paper. He was the first person to apply the now well-known terms _positive_ and _negative_ to photographic images, and to imprint them upon glass prepared by the deposit of a sensitive film. He also paved the way for Sir George Stokes's discovery of fluorescence, by his addition of the lavender rays to the spectrum, and by his announcement in 1845 of "epipolic dispersion," as exhibited by sulphate of quinine. Several other important researches connected with the undulatory theory of light are embodied in his treatise on "Light" published in the _Encyclopaedia metropolitana_. Perhaps no man can become a truly great mathematician or philosopher if devoid of imaginative power. John Herschel possessed this endowment to a large extent; and he solaced his declining years with the translation of the _Iliad_ into verse, having earlier executed a similar version of Schiller's _Walk_. But the main work of his later life was the collection of all his father's catalogues of nebulae and double stars combined with his own observations and those of other astronomers each into a single volume. He lived to complete the former, to present it to the Royal Society, and to see it published in a separate form in the _Philosophical Transactions_, vol. cliv. The latter work he left unfinished, bequeathing it, in its imperfect form, to the Astronomical Society. That society printed a portion of it, which serves as an index to the observations of various astronomers on double stars up to the year 1866. A complete list of his contributions to learned societies will be found in the Royal Society's great catalogue, and from them may be gathered most of the records of his busy scientific life. Sir John Herschel met with an amount of public recognition which was unusual in the time of his illustrious father. Naturally he was a member of almost every important learned society in both hemispheres. For five years he held the same office of master of the mint, which more than a century before had belonged to Sir Isaac Newton; his friends also offered to propose him as president of the Royal Society and again as member of parliament for the university of Cambridge, but neither position was desired by him.