tween that and the innermost ring, of less than 3 thousand miles, and that second ring is nearly 20 thousand miles in breadth, leaving a space between it and Saturn, of something more than 30 thousand miles. They are rounded at their edges, and extend north and south, about 4500* miles, and are supposed to be equally dense with the planet, and to revolve around it in about 10 hours.

Great inequalities are observable in different parts of the rings, which La Place considers as contributing to render their motions more stable than they would otherwise be.

Besides the rings, seven satellites attend Saturn. The nearest revolves in about 22 hours, at about 47 thousand miles distance from the largest ring. The remotest is more than 2 millions of miles distant from the planet, and revolves in about 80 days. The other five, at intermediate distances and periods. Their magnitudes are various: from four times the magnitude of our Moon, to about the magnitude of the Earth; and their densities are like their primary.

An engraving of Saturn will be found on Plate i. Figure 7.

Organs of vision like ours, enjoying a cloudless winter evening sky in Saturn, would behold as splendid and magnificent a scene, as our imagination can well form in a physical universe. But such organs of vision there, would be unable to discern the Earth without a telescope. "There is not, perhaps," says Dr.

What is the breadth of the innermost rings? What is their supposed thickness? What is the period of their rotation? What inequalities are discoverable in the rings? What is the utility of these inequalities?

How many satellites has Saturn? What is the period in which the nearest revolves? What is its distance from one ring? In what period does the most remote satellite revolve?—at what distance? What are their magnitudes ?-densities?

How would the evening sky appear in Saturn.

* Herschel, as quoted by Bonnycastle ?*

Herschel, "another object in the heavens that presents us with such a variety of extraordinary phenomena as the planet Saturn; a magnificent globe, encompassed by a stupendous double ring; attended by seven satellites; ornamented with equatorial belts; compressed at the poles; turning on its axis; mutually eclipsing its rings and satellites, and eclipsed by them; the most distant of the rings also turning upon its axis, and the same taking place with the remotest of the satellites; all the parts of the system of Saturn occasionally reflecting light to each other; the rings and the moons illuminating the nights of the Saturnian; the globe and the satellites enlightening the dark parts of the rings; and the planet and rings throwing back the Sun's beams upon the moons, when they are deprived of them, at the line of their conjunction."

CHAPTER VII.

HERSCHEL.

IN 1781, a new planet was discovered by Herschel, whose name it deservedly bears. It is like a star of the sixth magnitude to the naked eye, and seems slightly tinged with blue. Its apparent diameter is only 4 seconds, and its real diameter 35 thousand miles. Its density is equal to water. The time of its rotation unknown, but its period of revolution round the Sun, is almost 84 years, at the vast distance of 1800 millions of miles. It moves at the rate of about 15 thousand miles an hour, and receives from the Sun only one three hundred and sixtieth pari of the light the Earth enjoys.

It has before been intimated, that light and caloric seem not to be governed by the same laws. It cannot therefore be known, what amount of heat and fertility exist in any other planet but

When was Herschel discovered? What is its apparent diameter?-real diameter ?-density ?-period of rotation ?-revolution ?-rate the hour?-distance from the Sun?-comparative light?

Are light and caloric governed by the same laws? What hypothesis respecting life in other planets is here introduced?

the Earth. Life, adapted to its location, and analogous to vegetable, animal, and intellectual life, on the Earth; though entirely diverse in most of its circumstances from life here; may exist in other planets, and be immeasureably diffused in the material universe.

HERSCHEL'S SATELLITES.

SIX satellites attend the protracted journey of this most distant planet which has yet been discovered. The nea.est, is about as remote from Herschel, as the Moon from the Earth, and performs its revolution in between five and six days. The most distant is 14 millions of miles from its primary, and is 107 days in performing a revolution. Their densities are supposed to be like that of Her schel; but their orbits, unlike the orbits of all the other satellites, are nearly at right angles with the orbit of the primary, as though our Moon were to revolve from south east to north west, round the Earth.

Doubtless, these satellites exhibit the Creator's wisdom and benevolence, like his other works. The fact, that they may be revolving in a way to have some of them always above the horizon, and always half enlightened as seen at Herschel, might create more admiration in us, if we more minutely knew their circum

stances.

The scale on the frontispiece, divided into 200 parts, gives about the proportionate distances of planets, without the high enumeration of figures. Perhaps other planets, and some more distant than these, may yet be discovered.

Tabular views of the solar system and of the satellites are subjoined. For the greater densities of the Earth and the Moon, than has commonly been assigned them, we have the authority of Playfair, Cavendish, and Bakewell.

How many satellites attend Herschel? What are the extremes of their distances? What are their periods of revolution? How does their revolution differ from other satellites?

Where Tables are introduced in this work, the captions of the different columns, will suggest appropriate questions to Instructers and others.