To Wilhelm Struve belongs the credit of showing the disc-theory to be untenable, and of demonstrating that Herschel had abandoned it. This he was able to do after a perusal of Herschel’s papers, presented to him by John Herschel. Having demonstrated this, he undertook a series of investigations which resulted in his famous theory of the Universe. This was published in his work ‘Études d’Astronomie Stellaire,’ which was published in 1847. His researches were based on the star-catalogues of Bessel, Piazzi, and others; and dealing with 52,199 stars, he discussed the number of stars in each zone of Right Ascension. He found, in the words of Mr Gore, “that the numbers increase from hour i to hour vi, where they attain a maximum. They then diminish to a minimum at hour xiii, and rise to another but smaller maximum at hour xviii, again decreasing to a second minimum at hour xxii. As the hours vi and xviii are those crossed by the Milky Way, the result is very significant.” He concluded the Galaxy to be produced by a collection of irregularly-condensed clusters, the stars condensed in parallel planes. Next, he considered the Universe as perhaps infinitely extended in the direction of the Galaxy, and accordingly he put forward the idea that the light from the fainter and more distant stars was extinguished in its passage through the ether of space, which he regarded as imperfectly transparent. The theory, as Struve propounded it, was disposed of by Sir John Herschel, who remarked that we were not permitted to believe that at one part of the sky our view was limited by extinction, while at another a clear view right through the Galaxy could be had; and by _Robert Grant_ (1814-1892), director of the Glasgow Observatory, who showed that, were the theory true, the Galaxy should present a uniform appearance throughout its course. On the whole, Struve’s theory was no improvement on Herschel’s; for, as Encke pointed out, Struve’s theory was built on five assumptions, all of which were questionable.