It may appear somewhat presumptuous to place Uranus, a planet which it required the telescope and the eye of a Herschel to discover, in a list of objects for the opera-glass. But it must not be forgotten that Uranus was seen certainly several, and probably many, times before Herschel's discovery, being simply mistaken, on account of the slowness of its motion, for a fixed star. When near opposition, Uranus looks as bright as a sixth-magnitude star, and can be easily detected with the naked eye when its position is known. With an opera-glass (and still more readily with a field-glass) this distant planet can be watched as it moves deliberately onward in its gigantic orbit. Its passage by neighboring stars is an exceedingly interesting phenomenon, and it is in this way that you may recognize the planet. On the evening of May 29, 1888, I knew, from the co-ordinates given in the Nautical Almanac, that Uranus was to be found a short distance east of Mars, which was then only a few degrees from the well-known star Gamma Virginis. Accordingly, I turned my opera-glass upon Mars, and at once saw a star in the expected position, which I knew was Uranus. But there were other small stars in the field, and, supposing I had not been certain which was Uranus, how could I have recognized it? The answer is plain: simply by watching for a night or two to see which star moved. That star would, of course, be Uranus. The accompanying cuts will show the motions of Mars and Uranus with respect to neighboring stars at that time, and will serve as an example of the method of distinguishing a planet from the fixed stars by its change of place. In the first cut we have the two planets and three neighboring stars as they appeared on May 29th. These stars were best seen with a field-glass, although an opera-glass readily showed them. [Illustration: MARS AND URANUS, MAY 29, 1888.] [Illustration: MARS AND URANUS, JUNE 1, 1888.] [Illustration: MARS AND URANUS, JUNE 6, 1888.] On June 1st the relative positions of the planets and stars were as shown in the second cut. A glance suffices to show that not only Mars but Uranus also has shifted its position with respect to the three immovable stars. This change of place alone would have sufficed to indicate the identity of Uranus. To make sure, the inexperienced observer had only to continue his observations a few nights longer.