_Schiaparelli’s Results._—Mercury was displayed under several advantages in the morning twilight of November 1882, and I made a series of observations with a 10-inch reflector, power 212. Several dark markings were perceived, and a conspicuous white spot. The general appearance of the disk was similar to that of Mars, and I forwarded a summary of my results to Prof. Schiaparelli, of Milan, who favoured me with the following interesting reply:— “I have myself been occupied with this planet during the past year (1882). You are right in saying that Mercury is much easier to observe than Venus, and that his aspect resembles Mars more than any other of the planets of the solar system. It has some spots which become partially obscured and sometimes completely so; it has also some brilliant white spots in a variable position. As I observe the planet entirely by day and near the meridian I have been able to see its spots many times, but not always with the necessary distinctness to make drawings sufficiently reliable to serve as a base for a rigorous investigation. It is remarkable that the views taken near superior conjunction have been more instructive for me than those taken when the disk is near dichotomy, the defect in diameter being compensated by the possibility of seeing nearly all the disk, which, under those conditions, is more strongly illuminated. I believe that by instrumental means, such as our 8½-inch refractor at Milan gives, it is possible to prove the rotation-period of Mercury and to gain a knowledge of the principal spots as regards the generality of their forms. But these spots are really very complicated, for, besides the difficulties attending their observation, they are extremely variable.” Prof. Schiaparelli used an 8½-inch refractor in this work, and was able, under some favourable conditions, to apply a power of 400. The outcome of his researches, encouraged since 1882 by the addition of an 18-inch refractor to the appliances of his Observatory, has been recently announced in the curious fact that the rotation of Mercury is performed in the same time that the planet revolves round the Sun! If this conclusion is just, Mercury constantly presents one and the same hemisphere to the Sun, and the behaviour of the Moon relatively to the Earth has found an analogy. But these deductions of the eminent Italian astronomer require corroboration, and this is not likely to be soon forthcoming owing to the obstacles which stand in the way.