38

THE BEAUTY OF THE HEAVENS.

distinguished from the other planets by the extraordinary appendage of his vastluminous ring.

Although, through a common telescope, Saturn seems to be surrounded butby one broad ring, a telescope of high magnifying power shews that there areat least two rings, lying in the same plane, and forming two distinct con-centric circles about the planet, the ring which is nearest to him being muchbroader than the outer one, with a well defined space between them. Theinnermost edge of the nearest ring is nearly 4,000 miles from the body ofSaturn , leaving a visible space, through which some of the fixed stars have beenseen, between the planet and the ring. The breadth of the two rings together,is about 30,000 miles. Herschel is of opinion that these rings are solid, sincethey not only reflect the sun’s light, but also throw a strong shadow on thoseparts of the planet from which they intercept it.

The two rings rotate together about the planet, but are about thirteenminutes longer in performing their rotation than Saturn is in making his revo-lution on his own axis. The surfaces of the rings are permanently at rightangles with the axis of the planet, which is considerably inclined to its orbit.

The remarkable depression at the poles of Saturn is, in part, attributed. tohis quick revolution upon his axis ; in part, also, to the attraction existingbetween his body and his ring, which must constantly lessen the gravity of hisequatorial parts.

The upper figure of the scene represents a telescopic view- of the planet,with its rings and satellites. The small figure in the lower part of the scene,shews the planet and satellites at their general apparent ^distances from itsbody.

Before the invention of the telescope, the planet Saturn held no particularrank in the heavens, beyond that distinction which the slowness, yet regularityof its motion, and its steady brilliancy rendered remarkable. Its singularity ofappearance was first observed by Galileo in 1610: his discoveries in Jupiter and Saturn were the first fruits of his invention of the telescope. He describedthis planet as consisting of three globes—one large, with a smaller one on eachside. He veiled his discovery in a Latin sentence, which he transposed, thathis observation might remain secret, and yet afford him, at some future time,the means of establishing his claim to the honour of the discovery. Huygens ,also a learned astronomer , and contemporary with Galileo , actively continuedthe observations, and completed the discovery, by a full explanation of thephenomena of the ring, in substance precisely as it is understood by astronomersof the present day. The explanation was briefly thus: that the planet, in itscourse round the sun, holding its ring, as it were, always in the same position,as regards its axis of rotation, and being always seen from the earth within alimited obliquity, necessarily assumed a limited variety of oval forms—gra-dually contracting from a certain ellipticity to an almost imperceptible line, andagain expanding till it resumed its maximum of ellipticity.