Logs of wood floating in a pond approach each other, and afterwards
remain in contact. The wreck of a ship, in a smooth sea after a storm,
is often seen gathered into heaps. Two bullets or plummets, suspended by
strings near to each other, are found by the delicate test of the
torison balance to attract each other, and therefore not to hang quite
perpendicularly. A plummet suspended near the side of a mountain,
inclines towards it in a degree proportioned to its magnitude; as was
ascertained by the wellknown trials of Dr. Maskeleyne near the mountain
Skehalion, in Scotland. And the reason why the plummet tends much more
strongly towards the earth than towards the hill, is only that the earth
is larger than the hill. And at New South Wales, which is a point on our
globe nearly opposite to England, plummets hang and fall towards the
centre of the globe, exactly as they do here, so that they are hanging
up and falling towards England, and the people there are standing with
their feet towards us. Weight, therefore, is merely general attraction
acting every where. It is owing to this general attraction that our
earth is a globe. All its parts being drawn towards each other, that is,
towards the common centre, the mass assumes the spherical or rounded
form. And the moon also is round, and all the planets are round; the
glorious sun, so much larger than all these, is round; proving, that all
must at one time have been fluid, and that they are all subject to the
same law. Other instances of roundness from this cause are--the
particles of a mist or fog floating in air; these mutually attracting
and coalescing into larger drops, and forming rain; dew drops; water
trickling on a duck's wing; the tear-dropping from the cheek; drops of
laudanum; globules of mercury, like pure silver beads, coalescing when
near, and forming larger ones; melted lead allowed to rain down from an
elevated sieve, which cools as it descends, so as to retain the form of
its liquid drops, and become the spherical shot lead of the sportsman.
The cause of the extraordinary phenomenon, which we call attraction,
acts at all distances. The moon, though 240,000 miles from the earth, by
her attraction raises the water of the ocean under her, and forms what
we call the tide. The sun, still farther off, has a similar influence;
and when the sun and moon act in the same direction, we have the spring
tides. The planets, those apparently little wandering points in the
heaven, yet affect, by their attraction, the motion of our earth in her
orbit, quickening it when she is approaching them, retarding it when she
is receding.--_Arnott's Natural Philosophy._
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