times greater than that experienced from a full moon.

Tutor. So much greater is our meridian light than this, that during the sun's absence behind a cloud, when the light is much less strong than when we behold him in all his glorious splendour, it is reckoned that our day-light is 90,000 times greater than the light of the moon at its full. But Saturn has several

James.

moons, I believe?

Tutor. He is attended by seven satellites, or moons, whose periodical times differ very much; the one nearest to him performs a revolution round the primary planet in 22 hours and a half; and that which is most remote takes 79 days and 7 hours for his monthly journey; this last satellite is known to turn on its axis, and in its rotation is subject to the

same law which our moon obeys, that is, it revolves on its axis in the same time in which it revolves about the planet.

Besides the seven moons, Saturn is encompassed with two broad rings, which are probably of considerable importance in reflecting the light of the sun to that planet; the breadth of the inner ring is 20,000 miles, that of the outer ring is 7,200 miles, and the vacant space between the two rings is 2839 miles. These rings give Saturn a very different appearance from any of the other planets. The an

turn as seen through a good telescope. On the supposition that Saturn was the most remote planet of our system, he is thus described by Mallet, in his Excursion:

Last, outmost Saturn walks his frontier round, The boundary of worlds, with his pale moons, Faint glimm'ring through the gloom which night has thrown

Deep-dyed and dead o'er this chill globe forlorn : An endless desert, where extreme of cold Eternal sits, as in his native seat,

On wintry hills of never-thawing ice.

Such Saturn's earth; and even here the sight,
Amid these doleful scenes, new matter finds

Of wonder and delight! a mighty ring!

James.

Is it known of what na

ture the ring is?

Tutor. Dr. Herschel thinks it no less solid than the body of the planet itself, and he has found that it casts a strong shadow upon the planet. The light of the ring is brighter than that

of the planet; for the ring appears sufficiently bright for observation at times when the telescope scarcely affords light enough to give a fair view of Saturn.

Charles. Is it known whether Saturn turns on its axis?

Tutor. According to Dr. Herschel it has a rotation about its axis in 12 hours 134 minutes: this he computed from the equatorial diameter in the proportion of 11 to 10. Dr. Herschel has also discovered, that the ring, just mentioned, revolves about the planet in 10 hours and a 4, which is also the time of the planet's rotation on its axis.

CONVERSATION XXIII.

Of the Herschel Planet.

TUTOR. We have but one other planet to describe, that is the Herschel. James. Was it discovered by Dr. Herschel?

Tutor. It was, on the 13th of March, 1781; and therefore by many astronomers it is denominated the Herschel planet: though, by the docter himself, it was named the Georgium Sidus, or Georgian Star, in honour of his late majesty George the Third, who was for many years a liberal patron to this great and most indefatigable astronomer. Foreign astronomers usually call this planet Uranus.