A tumbler filled with water, may be whirled by a string vertically round the head, without any danger of the water falling out of it. Those parts of the Earth that come successively OPPOSITE to the Moon, perform a much larger circle round the centre of gravity, than the parts immediately UNDER the Moon: hence the waters opposite the Moon are THROWN OFF, as it were, by their centrifugal motion, and rise above the common level, as well as the waters exposed to the Moon’s immediate attraction; thus two tides are produced in 25 hours, opposite to each other; and by the Earth turning through those protuberances, its waters rise and fall.
The Sun would produce two small, but similar tides, if the Earth had no Moon; therefore at the full of the Moon the Sun’s centrifugal tide being reinforced by the Moon’s attraction, and the Moon’s centrifugal tide being also assisted by the Sun’s attraction, spring tides take place at the full, as well as at the change, of the Moon.
☞ This Scene also receives collateral assistance, exhibiting and explaining the setting of the tides in all the large oceans and the principal seas of the Earth.
This displays the whole Copernican or Solar System, with every planet and satellite in diurnal and annual motion! With awe and deference I offer this daring but humble transcript of creation! Enough, if one idea can be added, to the ingenuous mind, of the attributes and perfections of the Deity.
The SUN, a huge globe of fire (957,942 miles diameter, and consequently a million times as large as our Earth, and intended to give light, heat, and vegetation, to seven primary and at least eighteen secondary worlds) is placed in the centre of the system; and by spots on his disk is discovered to turn on his axis in about 25 of our days. These spots cannot be permanently fixed, because they are frequently altering in their shape, situation, number, &c. tho’ some have supposed they have seen small indentations on the edge of the Sun, as the spots have passed it, and conjectured that a fluid matter surrounded a dark nucleus, which sometimes becoming bare, might occasion the transient appearance and disappearance of the spots.
MERCURY is the first planet in the order of the system; about 3498 miles diameter: he moves round the Sun with the greatest velocity of any of the Planets familiar to our system (as being nearest the Sun) in about 88 of our days; at the rate of 110,680 English miles every hour, but the angle of his distance from the Sun, as seen by us, is so small, that unless by the telescope, we can seldom discern him[2]; (and even then an equatorial instrument to direct to its place, as indicated by the Ephemeris, will be requisite;) and when we do, it is for so short a time, and in twilight, that we can discover no spots on his face, and therefore to this hour know nothing of the length of his days and nights: we see him partially enlightened like the Moon, sometimes like a small crescent, in other situations half enlightened, and sometimes gibbous or oval, and are therefore certain he derives his light from the Sun, as she does: so that no doubt he is a fellow world, with inhabitants adapted to the heat of his situation: altho’ this heat is seven times as great as that of the Earth. He is not much larger than the Moon. Our Earth, viewed from Mercury, must appear much larger and more luminous than any of the Planets, except Venus, appears to us.