_Period &c._—Neptune revolves round the Sun in 60,126 days, which is equal to rather more than 164½ of our years. His mean distance from the Sun is 2,792,000,000 miles, and his usual diameter 2″·7. He exceeds Uranus in dimensions, his real diameter being 37,000 miles. _Observations._—Our knowledge of this distant orb is extremely limited, owing to his apparently diminutive size and feebleness. No markings have ever been sighted on his miniature disk, and we can expect to learn nothing until one of the large telescopes is employed in the work. No doubt this planet exhibits the same belted appearance as that of Uranus, and there is every probability that he possesses a numerous retinue of satellites. In dealing with an object like this small instruments are useless; they will display the disk, and enable us to identify the object and determine its position if necessary, but beyond this their powers are restricted by want of light. _Supposed Ring._—Directly the new planet was discovered, Mr. Lassell turned his large reflector upon it and sought to learn something of its appearance, and possibly detect one or more of its satellites. On October 3 and 10, 1846, he was struck with the appearance of the disk, which was obviously not perfectly spherical. He subsequently confirmed this impression, and concluded that a ring, inclined about 70°, surrounded the planet. Prof. Challis supported this view, but later observations in a purer sky led Mr. Lassell to abandon the idea. Thus the ring of Neptune, like the ring of Uranus, though apparently obvious at first, vanished in the light of more modern researches. _The Satellite._—But if Mr. Lassell quite failed to demonstrate the existence of a ring, he nevertheless succeeded in discovering a satellite belonging to the planet. This was on Oct. 10, 1846. The new satellite was found to have a period of 5^d 21^h 3^m, and to be situated about 220,000 miles distant from the planet. Its apparent star mag. is 14, and at max. elongation it extends its excursions to 18″ on either side of its primary. Compared with the other satellites of our system the one attending Neptune must be excessive in regard to size, or it could not be discerned at the vast distance separating it from the Earth. [Illustration: Fig. 45. Apparent Orbit of the Satellite of Neptune, as seen in an Inverting Telescope. (The small circle in the above diagram represents the planet, the arrows show the direction of motion, and the figures indicate the interval from the time of last North-east elongation.)]