the inhabitants of the earth, according to their different situations. Charles. At the poles, the matter is, I suppose, still different.

Tutor.

There one half of the ecliptic never sets, and the other half never rises; consequently, the sun continues one half year above the horizon, and the other half below it. The full moon being always opposite to the sun, can never be seen by the inhabitants of the poles, while the sun is above the horizon. But all the time that the sun is below the horizon, the full moon never sets. Consequently, to them the full moon is never visible in their summer; and in their winter they have her always before and after the full, shining for 14 of our days and nights without intermission. And when the sun is depressed the lowest under the horizon,

then the moon ascends with her

highest altitude.

James. This indeed exhibits in a high degree the attention of Providence to all his creatures. But if I understand you, the inhabitants of the poles have in their winter a fortnight's light and darkness by turns?

Tutor. This would be the case, for the whole six months that the sun is below the horizon, if there were no refraction,* and no substitute for the light of the moon. But by the at mosphere's refracting the sun's rays, he becomes, visible a fortnight sooner, and continues a fortnight longer in sight, than he would otherwise do were there no such property belong-> ing to the atmosphere. And in those parts of the winter, when it would

The subject of refraction will be very particu larly explained when we come to Optics.

be absolutely dark in the absence of the moon, the brilliancy of the Aurora Borealis is probably so great as to afford a very comfortable degree of light. Mr. Hearne, in his travels near the polar circle, has this remark in his journal: "December 24. The days were so short, that the sun only took a circuit of a few points of the compass above the horizon, and did not, at its greatest altitude, rise half way up the trees. The brilliancy of the Aurora Borealis, however, and of the stars, even without the assistance of the moon, made amends for this deficiency, for it was frequently so light all night, that I could see to read a small print.'

دو

These advantages are poetically

described by our Thomson:

By dancing meteors then, that ceaseless shake
A waving blaze refracted o'er the heavens,

And vivid moons, and stars that keener play
With double lustre from the glossy waste,
Ev'n in the depth of polar night, they find
A wondrous day; enough to light the chase,
Or guide their daring steps to Finland fairs.

WINTER, I. 859.

CONVERSATION XVIII.

Of Mercury.

TUTOR. Having fully described the earth and the moon, the former a primary planet, and the latter its attendant satellite, or secondary planet, we shall next consider the other planets, in their order, with which, however, we are less interested.

Mercury, you recollect, is the planet nearest the sun; and Venus is the second in order. These are called inferior planets.

Charles. Why are they thus denominated?

Tutor. Because they both revolve