_Rotation-Period._—Below are given the times of rotation ascertained by some previous observers:— h m s 1665. J. D. Cassini 9 55 58 1672. ” 9 55 50 1692. ” (A)9 50 1708. J. P. Maraldi 9 56 48 1713. ” 9 56 1773. Sylvabelle 9 56 1779. (B)W. Herschel 9 54 53} to 9 55 40} 1779. ” (A)9 50 48 } to 9 51 45·6} 1786. (C)J. H. Schröter 9 55 33·6 ” ” 9 55 17·6 ” ” (A)9 50 27 1835. J. H. Mädler 9 55 26·5 ” G. B. Airy 9 55 21·3 1836. J. H. Mädler 9 55 23·5 1862. J. F. J. Schmidt 9 55 25·7 1866. ” 9 55 46·3 1873. O. Lohse 9 55 19·6 1880. J. F. J. Schmidt 9 55 34·4 ” ” (A)9 50 1881. W. F. Denning 9 48 ” ” 9 55 17·9 1883. ” (A)9 50 8·7 1885. G. W. Hough 9 55 37·4 ” ” (A)9 50 9 1886. A. Marth 9 55 40·6 1887. A. S. Williams:— Spots in 12° N. lat. 9 55 36·5 ” 4° N. lat. (A)9 50 40·1 ” 8° S. lat. (A)9 50 22·4 ” 30° S. lat. 9 55 17·1 1890. (D)W. F. Denning 9 55 39 A: Bright spots near the equator of Jupiter. B: Herschel’s observations embraced few rotations, and the periods he derived differed considerably. C: Schröter also alleges he saw spots return to the same part of the disk in 7^h 7^m, 7^h 36^m, and 8^h 1^m! D: From ten years’ observations of the red spot. The foregoing list is by no means complete, for, owing to the large number of recent determinations, I have thought it advisable to omit some of them.