Positive evidence that this is the case was obtained by Giovanni Celoria, now director of the Milan Observatory, in the course of a series of star-gauges at the north galactic pole. Using a small refractor, showing stars barely to the eleventh magnitude, he found he could see exactly the same number of stars as Herschel’s large reflector, indicating that increase of optical power will not increase the number of stars visible in that direction. Celoria’s observation can only be explained on the assumption that the Universe is limited in extent, as otherwise Herschel’s telescope should have shown more stars than Celoria’s, even granting an extinction of light,—a theory which Newcomb, Schiaparelli, and others have shown to be quite untenable. That the Universe is limited in extent is about all that is known for certain, although even this has been called in question, notably by E. W. Maunder and H. H. Turner. The problem of the construction of the heavens is by no means solved, although several more or less probable theories have been advanced. A series of investigations on stellar distribution, from 1884 to 1898, led Hugo Seeliger, director of the Munich Observatory, to some remarkable deductions. He believes the Universe to be flattened at the galactic poles. The Galaxy is the zone of stellar condensation, and he concludes the distance of the Solar System from the inner border of the zone to be 500 times the distance of Sirius, while the external border is 1100 times that distance. The Universe is finite in extent, its limits being about 9000 light years from the Solar System. In Seeliger’s opinion the extinction of light may come into play beyond our Universe, and prevent us seeing other collections of stars. The question of external universes is purely a hypothetical one, although there is undoubtedly much to be said in its favour. These universes have never been seen, and we can only speculate as to their existence. The last word on the subject is by Gore, in 1893, in his elaborate work, ‘The Visible Universe.’ He regards the Solar System as a system of the first order, and the Galaxy and its fellow-universes of the second. He makes a calculation of the possible distance of an external universe of his second order. He assumes the distance of the nearest universe from our Galaxy as proportional to that separating the Sun from α Centauri, and reaches the amazing conclusion that the distance of the nearest Galaxy is no less than 520,149,600,000,000,000,000 miles,—a distance which light, with its inconceivable velocity of 186,000 miles a second, would take almost ninety millions of years to traverse.