At nearly double the distance of Jupiter from the sun circles the second largest planet of our system, unique, so far as human knowledge goes, in the character of its appendages. The orbit of Saturn has a mean radius of 886,000,000 miles, but owing to its eccentricity, his distance may be diminished to 841,000,000 or increased to 931,000,000. This large variation may not play so important a part in his economy as might have been supposed, owing to the fact that the sun heat received by him is not much more than 1/100th of that received by the earth. The planet occupies twenty-nine and a half years in travelling round its immense orbit. Barnard's measures with the Lick telescope give for the polar diameter 69,770, and for the equatorial 76,470 miles. Saturn's polar compression is accordingly very great, amounting to about 1/12th. Generally speaking, however, it is not so obvious in the telescopic view as the smaller compression of Jupiter, being masked by the proximity of the rings. [Illustration: PLATE XXIV. Saturn, July 2, 1894. E. E. Barnard, 36-inch Equatorial.] Saturn is the least dense of all the planets; in fact, this enormous globe, nine times the diameter of the earth, would float in water. This fact of extremely low density at once suggests a state of matters similar to that already seen to exist, in all likelihood, in the case of Jupiter; and all the evidence goes to support the view that Saturn, along with the other three large exterior planets, is in the condition of a semi-sun. The globe presents, on the whole, similar characteristics to those already noticed as prevailing on Jupiter, but, as was to be expected, in a condition enfeebled by the much greater distance across which they are viewed and the smaller scale on which they are exhibited. It is generally girdled by one or two tropical belts of a grey-green tone; the equatorial region is yellow, and sometimes, like the corresponding region of Jupiter, bears light spots upon it and a narrow equatorial band of a dusky tone; the polar regions are of a cold ashy or leaden colour. Professor Barnard's fine drawing (Plate XXIV.) gives an admirable representation of these features as seen with the 36-inch Lick telescope. Altogether, whether from greater distance or from intrinsic deficiency, the colouring of Saturn is by no means so vivid or so interesting as that of his larger neighbour.