THE PLANET JUPITER.

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while the third, and the first (in a less degree), also affordindications of the appearance of certain large and moderatelybright oval forms, which appear from time to time (andpossibly with some approach to a regular periodicity) in theprincipal central belts. Of such larger egg-shaped markingsa regular succession, ranged across the disc at almost equalintervals, and separated by smaller and darker spaces, isoccasionally seen ; when the effect produced, as is shown ina considerable number of published drawings of the planet,closely resembles that of a series of arches in a bridge. Manyobservers so described what they saw in the years 1869-1871.*The writer of this lecture also observed the same appearanceto be remarkably distinct in the autumn of 1879.

We think that our readers will find it w'ell worth while tostudy all the drawings of Jupiter to which they may be ableto obtain access. A large number may be found in vols. xxxi.and xxxiv. of the Royal Astronomical Society ’s Monthly No-tices ; the latter volume containing a very fine series observed atParsonstown with the great reflector belonging to Lord Rosse ,as well as some drawn by Mr. Knobel. There are also manyexcellent pictures of the planet published iu the years 1871 and1872, in vols. ix. and x. of the Astronomical Register. Othersare to be found in the volumes of the Observatory ; while twoespecially beautiful woodcuts illustrate an important article inNature of January 5th, 1882.

In several of these numerous delineations of the planet’sappearance, some of the smaller bright or dark spots, to whichwe have previously referred, may be noticed; but in the secondof the three drawings in Plate VIII. it will be observed thatthe most remarkable feature is a large oblong spot in theupper half of the view, which has not only caused a greatamount of excitement and interest amongst astronomersduring the last four years, but has so far exercised thepublic mind that it has frequently been discussed in thecolumns of our daily newspapers.

* See drawings in Astronomical Register for April and November 1871.Also Popular Science Review, vol. ix., pp. 129 and 131. Slight indicationsof these markings are also shown in Fig . LXX., p. 309, of this lecture.

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