Tides

“Let m be the Moon, and E the Earth covered with water. As the Moon passes round the Earth, its solid and fluid parts are equally attracted by her influence according to their densities; but while the solid parts are at liberty to move only as a whole, the water obeys the slightest impulse, and thus tends towards the Moon where her attraction is the strongest. Consequently, the waters are perpetually elevated immediately under the Moon. If, therefore, the Earth stood still, the influence of the Moon’s attraction would raise the tides only as she passed round the Earth. But as the Earth turns on her axis every 24 hours, and as the waters nearest the Moon, as at a, are constantly elevated, they will, in the course of 24 hours, move round the whole Earth, and consequently from this cause there will be high water at every place once in 24 hours.” —Comstock, 1850

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