scattered through space with some approach to uniformity, Herschel was able to compute the extent to which his telescope penetrated into space; and, assuming that the Universe was finite and that his “gauging-telescope” was sufficiently powerful to completely resolve the Milky Way, he was enabled to sketch the shape and extent of the Universe. Thus Herschel concluded that the Universe extended in the direction of the Galaxy to 850 times the mean distance of stars of the first magnitude. In the direction of the galactic poles the thickness was only 155 times the distance of stars of the same magnitude. Herschel was thus enabled to sketch the probable form of the Universe, which he regarded as cloven at one of its extremities, the cleft being represented by the famous gap in the Milky Way. The Universe was, in fact, supposed to be a cloven disc, and the Milky Way was merely a vastly extended portion of it and not a region of actual clustering. On this theory the clusters and nebulæ were supposed to be galaxies external to the Universe. Even in 1785, however, Herschel believed that there were regions in the Milky Way where the stars were more closely clustered than others. “It would not be difficult,” he wrote in 1785, “to point out two or three hundred gathering clusters in our system.” Strange to say, Herschel’s original ideas regarding the Universe were accepted for many years by astronomical writers. Arago accepted Herschel’s original theory, unaware that he had in reality abandoned it, and he was followed by a host of French and English writers who did not take the trouble to read each of Herschel’s papers, merely quoting that of 1785, and believing that it represented his final ideas on the subject. Even Sir John Herschel seems to have been unaware that his father gave up the disc theory of the Universe. The famous German astronomer, Wilhelm Struve, after an exhaustive study of Herschel’s papers, was enabled to prove in 1847 that the theory had been abandoned by Herschel; and in England the late R. A. Proctor independently demonstrated the same thing. Meanwhile, supposing Herschel had not given up his theory, it would be quite untenable. After considering the fact that the brighter stars, down to the ninth magnitude, aggregate on the Milky Way, Mr Gore says: “As the stars are by hypothesis supposed to be uniformly distributed throughout every part of the disc, and as the limiting circles for stars to the eighth and ninth magnitudes fall well within the thickness of the disc, there is no reason why stars of these magnitudes should not be quite as numerous in the direction of the galactic poles as in that of the Milky Way itself. We see, therefore, that the disc theory fails to represent the observed facts, and that Struve and Proctor were amply justified in their opinion that the theory is wholly untenable, and should be abandoned.”