200l. an object-glass of 8 inches diameter made by the American firm of Alvan Clark, which was mounted equatorially and provided with a clock motion by Messrs. Cooke of York. With this instrument he observed between 1858 and 1860 the changes in the forms of the belts and spots on Jupiter, and the periodic disappearance of Saturn's rings in 1862 (cf. R. Astr. Soc. Notices). The publication in 1862 of Kirchhoff's interpretation of the Fraunhofer lines in the spectrum as showing the chemical constitution of the sun turned
Huggins's attention in a new and more fruitful direction. To his neighbour at Tulse Hill, William Allen Miller [q. v.], professor of chemistry at King's College, who had worked much on chemical spectroscopy, Huggins confided a scheme for applying Kirchhoff's methods to the stars, and asked Miller to join him in the research. Huggins and Miller devised a new instrument, a star spectroscope,
which enabled them to determine the chemical constitution of stars. They described their star spectroscope in the 'Philosophical Transactions of the Royal Society' for 1864, pp. 415-17. The light-dispersing portion of the apparatus consisted of two prisms of very dense and homogeneous flint glass made by Ross, which were attached to the 8-inch refractor. Mr. Rutherford in America had already devised similar apparatus quite independently. Miller and Huggins owed nothing to his invention. As a preliminary to work on the stars with this instrument it was necessary to have convenient maps of the spectra of terrestrial elements, and Huggins devoted a large part of 1863 to making twenty-four such maps with a train of six prisms. These were published in a paper read before the Royal Society in December of that year (Phil. Trans. 1864, cliv. 139). Earlier in 1863 Miller and Huggins had presented to the Royal Society the results of their first investigations with their star spectroscope in a paper on the 'Lines of the Spectra of some of the Fixed Stars' (Proc. Roy. Soc. 1863, xii. 444) ; this was followed by a more complete paper on the ' Spectra of some of the Fixed Stars' (Phil Trans. 1864, cliv. 413-35). The conclusion was that 'in plan of structure the stars, or at least the brightest of them, resemble the sun. Their light, like that of the sun, emanates from intensely white-hot matter, and passes through an atmosphere of absorbent vapours. With this unity of general plan of structure there exists a great diversity amongst the individual stars. Star differs from star in chemical constitution' (cf his addresses, Brit. Assoc. 4 Aug. 1866). On 29 Aug. 1864 Huggins made an important observation. Examination with the spectrum apparatus showed that the light from a certain planetary nebula in Draco was such as would emanate from a luminous gas, and hence it was to be concluded that so-called nebulae were not in all cases aggregations of stars too far distant to be resolved into their constituent units, as had hitherto been supposed. In a paper 'On the Spectra of some of the Nebulæ' (Phil. Trans. 1864, cliv. 437) Huggins showed that eight nebulae he had examined exhibited gaseity. This paper, by Huggins alone, was published as a supplement to the joint paper on the 'Spectra of the Fixed Stars,' and like the former papers was communicated by Dr. Miller, Huggins not being then a fellow of the Royal Society. He was elected a fellow in June 1865.
In May 1866 Huggins first subjected to spectroscopic examination a Nova, or new star, one having appeared in the constellation Corona Borealis. He suggested that, owing to some great convulsion, the star had been suddenly enveloped in flames of burning hydrogen (Proc. Roy. Soc. 1866, XV. 146). By 1866 ten papers in all had been published. In that year the Royal Society awarded a royal medal to Huggins for his researches. Miller, as a member of the council, was excluded from this honour, and his other engagements soon prevented him from working with Huggins by night, but in 1867 the gold medal of the Royal Astronomical Society was given to Huggins and Miller jointly for their work in astronomical physics. From to 1870 Huggins was one of the hon. secretaries of the Royal Astronomical Society, vice-president from 1870 to 1873, and from 1873 to his death, except for two years (1876-8) when he was president, was foreign secretary.
In the years following 1864 Huggins extended his series of observations of nebulae, examining amongst others the great nebula in Orion (cf. Phil. Trans. clvi. 381, clviii. 540 ; Phil. Mag. xxxi. 475 ; Proc. Roy. Soc. 1865, xiv. 39; Monthly Notices R.A.S. xxv. 155). From 1866 onwards he observed the spectrum of several comets as they appeared, and found the spectrum of Brorsen's comet of 1868 to indicate a chemical constitution different from that of the nebulae (cf. Proc. Roy. Soc. 1868, xvi. 386), whilst spectroscopic examination of the second
