The important tasks in progress at the Paris observatory have of late been singularly impeded by bad weather. During the latter half of 1882 scarcely four or five good nights per month were secured, and in December these were reduced to two.[25] Moreover, M. Thollon, who, according to his custom, arrived from Nice in June for the summer’s work, returned thither in September without having found the opportunity of making _one single_ spectroscopic observation. Yet within easy and immediate reach was a post, already in scientific occupation, where as General de Nansonty reported, ordinary print was legible by the radiance of the milky way and zodiacal light alone, and fifteen or sixteen Pleiades could be counted with the naked eye. At length Admiral Mouchez, the energetic director of the Paris observatory, convinced of the urgent need of an adjunct establishment under less sulky skies, issued to MM. Thollon and Trépied a commission of inquiry into telescopic possibilities on the Pic du Midi. Their stay lasted from August 17th, to September 22d, 1883, and their experiences were summarised in a note (preliminary to a detailed report) published in the “Comptes Rendus” for October 16th, glowing with a certain technical enthusiasm difficult to be conveyed to those who have never strained their eyes to catch the vanishing gleam of a “chromospheric line” through a “milky” sky, and dim and tremulous air. The definition, they declared, was simply marvellous. Not even in Upper Egypt had they seen anything like it. The sun stood out, clean-cut and vivid, on a dark blue sky, and so slight were the traces of diffusion, that, for observations at his edge the conditions approached those of a total eclipse. These advantages are forcibly illustrated by the statement that, instead of eight lines ordinarily visible in the entire spectrum of the chromosphere, more than thirty revealed themselves in the orange and green parts of it alone (Dto. F)! A fact still more remarkable is that prominences were actually seen, and their forms distinguished, though foreshortened and faint, on the very disc of the sun itself—and this not merely by such glimmering views as had previously, at especially favorable moments, tantalised the sight of Young and Tacchini, but steadily and with certainty. We are further told that, on the mornings of September 19th and 20th, Venus was discerned, without aid from glasses, within two degrees of the sun. These extraordinary facilities of vision disappeared, indeed, as, with the advance of day, the slopes of the mountain became heated and set the thin air quivering; but were reproduced at night in the tranquil splendor of moon and stars.