Herschel’s earlier idea that the nebulæ were external galaxies was long held by the majority of astronomers, in preference to his later and more advanced ideas. The supposed resolution of the nebulæ by Lord Rosse’s telescope gave support to this external galaxy theory. It was clearly shown, however, by _William Whewell_ (1794-1866) in 1853, and by _Herbert Spencer_ (1820-1903) in 1858, that the systematic distribution of the nebulæ in regard to the stars precluded the possibility of their being external galaxies. This was confirmed by the spectroscopic discovery of the gaseous nature of some of the nebulæ, and by the later researches of R. A. Proctor. Not only did Proctor make fresh discoveries, but it fell to him to clear away the erroneous ideas regarding the construction of the heavens, and to put the study on a new basis. In 1870 Proctor plotted on a single chart all the stars, to the number of 324,198, contained in Argelander’s ‘Durchmusterung’ charts. This work gave the death-blow to the “disc-theory.” In his own words, “In the very regions where the Herschelian gauges showed the minutest telescopic stars to be most crowded, my chart of 324,198 stars shows the stars of the higher orders (down to the eleventh magnitude) to be so crowded, that by their mere aggregation within the mass they show the Milky Way with all its streams and clusterings. It is utterly impossible that excessively remote stars could seem to be clustered exactly where relatively near stars were richly spread.” Proctor showed also that in all probability the stars composing the nebulous light of the Galaxy are much smaller than the brighter stars, and not at such a great distance as their faintness would lead us to suppose,—a conclusion confirmed by the work of Celoria. Proctor was not so fortunate in theorising as in direct investigation. He thought that the Magellanic clouds were probably external galaxies; and further, he put forward the idea that the Milky Way is a spiral, the gaps and coal-sacks being due to loops in the stream, but neither of these ideas has found favour with astronomers. But the chief work accomplished by Proctor was a revision of our knowledge of the Universe, which he thus describes: “Within one and the same region coexist stars of many orders of real magnitude, the greatest being thousands of times larger than the least. All the nebulæ hitherto discovered, whether gaseous and stellar, irregular, planetary, ring-formed, or elliptic, exist within the limits of the Sidereal System.”