She is full of caverns and deep pits.]

59. If there were seas in the Moon, she could have no clouds, rains, nor

storms as we have; because she has no such Atmosphere to support the

vapours which occasion them. And every one knows, that when the Moon is

above our Horizon in the night time, she is visible, unless the clouds

of our Atmosphere hide her from our view; and all parts of her appear

constantly with the same clear, serene, and calm aspect. But those dark

parts of the Moon, which were formerly thought to be seas, are now found

to be only vast deep cavities, and places which reflect not the Sun’s

light so strongly as others, having many caverns and pits whose shadows

fall within them, and are always dark on the sides next the Sun; which

demonstrates their being hollow: and most of these pits have little

knobs like hillocks standing within them, and casting shadows also;

which cause these places to appear darker than others which have fewer,

or less remarkable caverns. All these appearances shew that there are no

seas in the Moon; for if there were any, their surfaces would appear

smooth and even, like those on the Earth.

[Sidenote: The Stars always visible to the Moon.]

60. There being no Atmosphere about the Moon, the Heavens in the day

time have the appearance of night to a Lunarian who turns his back

toward the Sun; and when he does, the Stars appear as bright to him as

they do in the night to us. For, it is entirely owing to our Atmosphere

that the Heavens are bright about us in the day.

[Sidenote: The Earth a Dial to the Moon.]

61. As the Earth turns round it’s Axis, the several continents, seas,

and islands appear to the Moon’s inhabitants like so many spots of

different forms and brightness, moving over it’s surface; but much

fainter at some times than others, as our clouds cover them or leave

them. By these spots the Lunarians can determine the time of the Earth’s

diurnal motion, just as we do the motion of the Sun: and perhaps they

measure their time by the motion of the Earth’s spots; for they cannot

have a truer dial.

[Sidenote: PLATE I.

Astronomy Explained Upon Sir Isaac Newton's Principles And made easy to those who have not studied mathematics · 第 57 / 275 题