The Melbourne reflector of 4-feet aperture performed very indifferently for some years, and little work was accomplished with it. Latterly its performance has been more satisfactory; excellent photographs of the Moon have been taken, and it has been much employed in observations of nebulæ. The speculum having recently become tarnished, it has been dismounted for the purpose of being repolished. The silver-on-glass reflector of 47·2-in. diameter, at the Paris Observatory, was used for some years by M. Wolf, who has also had the control of smaller telescopes. He was in a favourable position to judge of their relative effectiveness. In a lecture delivered at the Sardonne on March 6, 1886, he said:—“During the years I have observed with the great Parisian telescope I have found but one solitary night when the mirror was perfect.” Further on, he adds:—“I have observed a great deal with the two instruments [both reflectors] of 15·7 inches and 47·2 inches. I have rarely found any advantage in using the larger one when the object was sufficiently luminous.” M. Wolf also avers that a refractor of 15 inches or reflector of 15·7 inches will show everything in the heavens that can be discovered by instruments of very large aperture. He always found a telescope of 15·7-inch aperture surpass one of 7·9 inches, but expresses himself confidently that beyond about 15 inches increased aperture is no gain. The Washington refractor of 25·8 inches effected a splendid success in Prof. Hall’s hands in 1877, when it revealed the two satellites of Mars. But immediately afterwards these minute bodies were shown in much smaller instruments; whence it became obvious that their original discovery was not entirely due to the grasp of the 25·8-inch telescope, but in a measure to the astuteness displayed by Prof. Hall in the search. A good observer had been associated with a good telescope; and an inviting research having been undertaken, it produced the natural result—an important success. The same instrument, in the same hands, enabled the rotation-period of Saturn to be accurately determined by means of a white spot visible in December 1876 on the disk of the planet, and which was subsequently seen by other observers with smaller glasses. Good work in other directions has also been accomplished at Washington, especially in observations of double stars and faint satellites. But notwithstanding these excellent performances, Prof. Hall expressed himself in rather disparaging terms of his appliances, saying “the large telescope does not show enough detail.” He gave a more favourable report in 1888; for we find it stated that “the objective retains its figure and polish well. By comparison with several other objectives which Prof. Hall has had an opportunity of seeing during recent years, he finds that the glass is an excellent one.”