But we have now certain knowledge of the existence of more than 2 rings, and the system must be described as a multiple one. It is stated by Lalande that Short, the celebrated optician, perceived several concentric streaks on the outer ring. It is not known that Short left any record of his own relating to this. Between June 19 and 26, 1780, Sir W. Herschel perceived a slight dark streak close to the interior edge of the western ansa. It had disappeared on June 29, and no corresponding appearance at all was seen on the other ansa. In Dec. 1823 M. Quetelet, at Paris, with a Cauchoix achromatic of 10 inches aperture, thought he saw a division in the exterior ring. On Dec. 17, 1825, Capt. Kater, with a 6-inch Newtonian reflector, perceived in the exterior ring numerous black streaks very close to each other. On Jan. 16, 1826, with another telescope, the same observer saw similar markings, but as on Jan. 22, 1828, none whatever could be perceived, he concluded that they had no permanent existence. On April 25, 1837, Enckes, at Berlin, assured himself of the existence of a division in the exterior ring; on May 28 following he was able to procure measurements which shewed that the old ring was unequally divided, the wider portion lying outermost. On May 29, 1838, Di Vico, at Rome, perceived not only this division, but two similar divisions in the interior ring. t On Sept. 7, 1843, Lassell and Dawes saw a decided division in the exterior ring at both ends, but placed it near the outermost edge, thereby failing to agree with Encke's measurements of 1837. This subdivision of the exterior ring is now generally accepted ", and De La Rue's beautifully executed engraving (Fig. 98, Plate XII) conveys a good idea of it. • Astronomie, vol. iii. Paragraph 3228. 2nd ed., Paris, 1771. P Phil. Trans., vol. lxxxii. p. 8. 1792. a Mem. R. A. S., vol. iv. p. 388. 1831. Mem. R. A. S., vol. iv. p. 384. 1831. • Mathematische Abhandlungen der Königl. Akad. Wissenschaften Berlin, 1838, p. 5. t Month. Not., vol. vi. p. 12. u Jacob on the contrary expressed in unequivocal terms his conviction that the black mark or so-called division in the exterior ring was merely a depression. He was confident that it reflected the planet's shadow, shewing an apparent projection, such as every shadow falling The discovery of another curious and interesting feature has now to be dealt with. In 1838 Galle, in examining Saturn, noticed a gradual shading off of the interior bright ring towards the ball. He published a note of this observation, but little or no attention seems to have been paid to it *. On Nov. 11, 1850, G. P. Bond perceived a luminous appearance between the ring and the planet: subsequent observations by himself and his father shewed that this luminous appearance was neither more nor less than another ring. Neither of these observers could satisfactorily determine whether this dusky ring (as it soon came to be called) was actually in contact with the interior bright ring, but they thought it was not. Before the arrival of the American mail conveying intelligence of this new ring, Dawes had found it. On Nov. 29 he entered in his Journal the following remark: "After a few seconds of uncommonly sharp vision, I involuntarily exclaimed, 'Obvious.' There is a shading, like twilight, at the inner portions of the inner ring." This acute observer was not long in ascertaining the annular character of the "shading," and moreover he found (as did O. Struve also) that the dusky ring was occasionally divided into 2 or more concentric rings. This fact is not indicated in De La Rue's engraving, but the transparent nature of the entire ring is well shewn. On Dec. 3, Lassell, while on a visit to Dawes, saw 66 something like a crape veil covering a part of the sky within the inner ring" this observation was made in consequence of a hint given by Dawes as to what he himself had seen ". on a groove has. (Month. Not., vol. xvi. p. 126, March 1856; vol. xvii. p. 174, April 1857.) Hippisley and Watson disbelieved in a division, and adhered to the opinion that the mark is merely a mark, and that its breadth varies. Month. Not., vol. xiv. p. 163, March 1854; vol. xvi. p. 152, April 1856.) * Math. Abhandl. Königl. Akad. Wissenschaften Berlin, 1838, p. 7. See also Ast. Nach., vol. xxxii. No. 756. May 2, 1851; and Month. Not., vol. xi. p. 184. June 1851. ▾ Mem. Amer. Acad. of Arts and Sciences, vol. v., (N.S.), p. III. 1855. Month. Not., vol. xi. p. 23. Dec. 1830. A passage in Phil. Trans., vol. xxxii. p. 385, 1723, by Hadley, almost leads one to infer that he had seen the dusky ring, though without being able to make up his mind as to what it was. Hind, in Month. Not., vol. xv. p. 32, Nov. 1854, expresses his belief that a record of Picard's will fairly bear the interpretation that on June 15, 1673, he saw the dusky ring, with the like comprehension as Galle. |