Buffon's Natural History, Volume 01 (of 10): Containing a Theory of the Earth, a General History of Man, of the Brute Creation, and of Vegetables, Mineral, &c. &cBuffon, Georges Louis Leclerc, comte de
History
Buffon's Natural History, Volume 01 (of 10): Containing a Theory of the Earth, a General History of Man, of the Brute Creation, and of Vegetables, Mineral, &c. &c
Buffon, Georges Louis Leclerc, comte de
Natural history
4. At the time a body is put in motion by the force of impulsion, is it
not probable that it receives it obliquely, and, consequently, is
obliged to turn on its axis so much the quicker, as the obliquity of the
stroke will have been greater? If these questions should not appear
unreasonable, the theory, of which we have presented the outlines, will
cease to appear an absurdity.
Let us now pass on to something which more nearly concerns us, and
examine the figure of the earth, on which so many researches and such
great observations have been made. The earth being, as it appears by the
equality of its diurnal motion and the constancy of the inclination of
its axis, composed of homogeneous parts, which attract each other in
proportion to their quantity of matter, it would necessarily have taken
the figure of a globe perfectly spherical, if the motion of impulsation
had been given it in a perpendicular direction to the surface; but this
stroke having been obliquely given, the earth turned on its axis at the
moment it took its form; and from the combination of this impulsive
force, the attraction of the parts, there has resulted a spheroid
figure, more elevated under the great circle of rotation, and lower at
the two extremities of the axis, and this because the action of the
centrifugal force proceeding from the diurnal rotation must diminish the
action of gravity. Thus, the earth being homogeneous, and having
received a rotative motion, necessarily took a spheroidical figure, the
two axes of which differ a 230th part from each other. This may be
clearly demonstrated, and does not depend on any hypothesis whatever.
The laws of gravity are perfectly known, and we cannot doubt that
bodies attract each other in a direct ratio of their masses, and in an
inverted ratio, at the squares of their distances; so likewise we cannot
doubt, that the general action of any body is not composed of all the
particular actions of its parts. Thus each part of matter mutually
attracts in a direct ratio of its mass and an inverted ratio of its
distance, and from all these attractions there results a sphere when
there is no rotatory motion, and a spheroid when there is one. This
spheroid is longer or shorter at the two extremities of the axis of
rotation, in proportion to the velocity of its diurnal motion, and the
earth has then, by virtue of its rotative velocity, and of the mutual
attraction of all its parts, the figure of a spheroid, the two axes of
which are as 229 to 230 to one another.
Thus, by its original constituent, by its homogeneousness, and
independent of every hypothesis from the direction of gravity, the earth
has taken this figure of a spheroid at its formation, and agreeable to
mechanical laws: its equatorial diameter was raised about 6-1/2 leagues
higher than under the poles.
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