Hence with the planes of all the meridians converging at the pole, as one has just noted, it needs only a little reflection (even without the least tint of Geometry), to see that the earth could not be curved in the direction of the meridian, without it also being curved in the direction that is perpendicular to the meridian, and that consequently is it curved in all senses. From that it was easy to conclude that the plumb line, that is the line that is perpendicular to the surface of the Earth, and passing through the top of our head, changed direction to the same extent that one advanced along the meridian, and did not always remain parallel to it as a consequence, the surface of the earth was not a plane, but curved in the direction of the meridian. Also, Aristotle, who was a contemporary, or even a predecessor of several of the philosophers named above, established and proved the roundness of the earth in his second book on the sky, chapter xiv, by means of reasoning that was very solid, and very similar to what we are about to provide.įirst of all one noticed that among the stars that one saw turning round the earth, there were some that always stayed in the same place, or nearly so, and that consequently the entire celestial sphere turned around a fixed point in the sky one called this point the pole one noted very soon after, that while the sun found itself each day at its greatest elevation above our head, it was then constantly on the plane that passed through the pole and a plumb line one called this plane the meridian : one then observed that when one travelled in the direction of the meridian, the stars towards which one was travelling appeared to approach from above the head, and that the others by contrast appeared to move away from it and that furthermore these latter stars, in declining, entirely disappeared, and that others began to appear from the opposite side. Was already so advanced, one was still so ignorant of the form of the Earth for one will see that the earliest astronomical observations would have led one to know that it is round in every sense. Hence it is not plausible, it seems to me, that in a time in which astronomy → Had by their time already made great progress, as Thales, who preceded them, had predicted eclipses. But we will allow ourselves to doubt whether the great majority of the philosophers we have just named had such absurd ideas. This last opinion reminds one of that of the peoples of India, who believe the earth to be borne on four elephants. Anaximander, it is said, believed the earth to be like a column, Leucippus a cylinder, Cleanthes a cone, Heraclitus a skiff, Democritus a hollow disc, Anaximenes and Empedocles a flat disc, and finally Xenophanes of Colophon imagined it had an infinite root on which it carried itself. One may inform oneself about these in the Almagest of Riccioli and elsewhere. We will not go into any detail about the extravagant opinions that the ancients held, or that are attributed to them about the form of the Earth.
This important question has raised such a clamor in recent times, learned men – above all in France – have so occupied themselves with it, that we believe we must make it the subject of a specific article, without turning to the word Earth, which will otherwise provide us with plenty of material for other topics. Originally published as "Figure de la terre," Encyclopédie ou Dictionnaire raisonné des sciences, des arts et des métiers, 6:749–761 (Paris, 1756).įorm of the Earth. Ann Arbor: Michigan Publishing, University of Michigan Library, 2018. "Form of the Earth." The Encyclopedia of Diderot & d'Alembert Collaborative Translation Project. Paris, 1756.ĭ'Alembert, Jean-Baptiste le Rond. of "Figure de la terre," Encyclopédie ou Dictionnaire raisonné des sciences, des arts et des métiers, vol.
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