Deducting duplicate discoveries, Palisa carries off the palm for the largest number, for (up to the end of 1888) he had detected 68 minor planets. Then comes Peters with 47; Luther with 23; Watson with 22; Borelly with 15; Goldschmidt with 14; Hind with 10; and so on. The want of telescopes suitable and available for looking after minor planets tends now to hinder new discoveries. All the brighter ones have evidently been found; and, speaking generally, each new one is fainter than its predecessors, and consequently small telescopes are now incapable of doing the work. The following table will show this better than any argument:Mean & Star Mag. The above numbers are not, it is true, in perfect sequence, and it is not possible to complete the Table at present, but my meaning will be sufficiently clear. The figures in the column headed "Diameter" in the Table (see Book VI, post) are the results of calculations by Stone *. Photometric experiments made by Professor Stampfer of Vienna yielded somewhat similar results'. But both sets of figures are probably more relatively than absolutely accurate. Argelander Month. Not., vol. xxvii. p. 302. June 1867. 1 See Bruhns's De Planetis Minoribus, Berlin 1856, for details. Some physical investigations by Newcomb into the orbits of certain of these planets will be found in Mem. of the American Acad., vol. V., N.S., pp. 123-35: an abstract appears in Month. Not., vol. xxi. pp. 55-7. Dec. 1860. published some suggestions for determining the brightness of these planets. Pickering also has made a few endeavours in this direction". In Hornstein's opinion all the larger Minor Planets have now been found, and those having a greater diameter than 25 geographical miles are few in number. Omitting a few of comparatively larger size, he puts the general diameter of the bulk of them at from 5 to 15 miles °. Below are given the names of the only minor planets for the determination of whose places we as yet possess Tables. It is not likely that this list will ever be much enlarged, for the increase of late years in the number of these planets has severely taxed the patience of astronomical computers. By Becker-Tables for Amphitrite. By Brünnow:-Tables for Iris, Flora, Victoria. By Hansen:-Tables for Egeria. By Lesser:-Tables for Metis, Lutetia, Pomona. By Möller: Tables for Pandora. By Schubert:-Tables for Parthenope, Eunomia, Melpomene, Harmonia. m Month. Not., vol. xvi. p. 206. June 1856. Ast. Nach., vol. xlii. No. 996. Nov. 29, 1885. n Annals of the Observatory of Harvard College, 1879. Sitzungsberichte der Math. Naturwissenschaftlichen Classe der Kaiserlichen Akademie, vol. lxxxiv. pt. ii. p. 7. June 2, 1881. CHAPTER XI. JUPITER. 24 Period, &c.-Jupiter subject to a slight phase.-Its Belts.-Their physical nature.— First observed by Zucchi.-Dark Spots.-Luminous Spots.-The great Red Spot. The great White Spot.-Hough's observations.-Alleged Connection between Spots on Jupiter and Spots on the Sun.—Axial rotation of Jupiter.— Centrifugal force at its Equator.-Luminosity of Jupiler.-Its Apparent Motions.-Astrological influences.—Attended by 4 Satellites.-Are they visible to the Naked Eye ?—Table of them.-Eclipses of the Satellites.-Occultations.Transits.— Peculiar aspects of the Satellites when in transit.—Singular cir· cumstance connected with the interior ones.—Instances of all being invisible.— Variations in their brilliancy.—Observations of Eclipses for determining the longitude.-Practical difficulties.-Römer's discovery of the progressive transmission of light.-Mass of Jupiter.--The "Great Inequality."-Tables of Jupiter. JUP ́UPITER, the largest planet of our system, revolves round the Sun in 4332.6 or 11.86, at a mean distance of 483,288,000 miles. The eccentricity of its orbit is 0.048, so the planet may recede from the Sun to 506,563,000 miles, or approach it to within 460,01 3,000 miles. The planet's apparent diameter varies between 49.9′′ in opposition and 30-4′′ in conjunction, being 40.13′′ at its mean distance, according to very elaborate measurements by Main. The equatorial diameter is 88,400 miles or thereabouts. The compression is greater than that of any other planet except Saturn, and amounts, according to the trustworthy observations of Main, to All the values of this quantity are closely in accord: e.g. Lassell gave 1785. Important modern delineations of Jupiter will be found as follows:-Month. Not., vol. xxxi. p. 34. Dec. 1870 (Brown ing); vol. xxxiv. p. 235. March 1874 (the Earl of Rosse); vol. xxxiv. p. 403. June 1874 (Knobel). |