David Gregory (mathematician)

“Newtonian Astronomy @Astronomy at the Edward Worth Library (see David Gregory under The Reception of Newtonian Astronomy)”

“Newton and Astronomers @Newton at the Edward Worth Library”

“Gregory [Gregorie, David] @The Galileo Project, Rice University.”

“Gregory, David, 1659-1708 (professor of mathematics, University of Edinburgh, and Savilian Professor of Astronomy, University of Oxford) @University of Edinburgh Archives Online”

“David Gregory @MacTutor History of Mathematics Archive”

“Wren, Christopher”

“History of science”

“History of mathematics”

“[T]he Opinion of the Ancients concerning Gravity... they were perswaded that Gravity was not an affection of Terrestrial Bodies only, but of the Celestial also, that all Bodies gravitate towards one another; and that the Planets are retained in their Orbits by the force of Gravity, and lastly, that the Gravity of the Planets towards the Sun are reciprocally as the Squares of their Distances from it. What the industry and skill of the Moderns have added to these inventions of the Ancients, the following Pages do declare at large.”

“[U]niversally, the Weights which generate all Tones in Strings, are reciprocally as the Squares of the lengths of Strings of equal Tension, producing the same sound in any Musical Instrument.”

“[S]o also they were not unacquainted with the Law and Proportion which the action of Gravity observ'd according to the different Masses and Distances. For that Gravity is proportional to the Quantity of Matter in the heavy Body, Lucretius does sufficiently declare, as also that what we call light Bodies, don't ascend of their own accord, but by the action of a force underneath them, impelling them upwards, just as a piece of Wood is in Water; and further, that all Bodies, as well the heavy as the light, do descend in vacuo, with an equal celerity.”

“Lucretius and those whom he followed, believ'd that all Bodies did Gravitate towards the Matter placed around them, and that every single Body was carried by the more prevailing Gravity, towards that region where there was most Matter.”

“From some things mention'd by Diogenes Laertius concerning Plato, which also are obscurely hinted at in his Timæus I am apt to believe with Galileo that the divine Philosopher suppos'd the Mundane Bodies, when they were first formed, were moved with a Rectilinear motion (by the means of Gravity,) but after that they had arrived to some determined places, they began to revolve by degrees in a Curve, the Rectilinear Motion being chang'd into a Curvilinear one.”

“[A]fterwards it diffused it self thro' the Italic Philosophy, the followers of which taught, that each Star was a World in the infinite Æthereal Space, containing Earth, Air and Æther; and that the Moon, not only was like our Earth, but inhabited by Animals of a larger size, and furnish'd with Plants of a more beautiful appearance.”

“These notions Anaximenes received from Anaximander, Anaximander from Thales himself, who was the Head and Founder of the Ionic Philosophy; and spread this opinion of the Gravity of the Fix'd Stars among his Sect.”

“[A]s we are told by Democritus these notions about the Sun and Moon are not to be ascrib'd to Anaxagoras as their original... He had them from his Master Anaximenes whose Opinion... was, that the Stars were of a fiery nature and substance, that there were also mingled with them certain Earthly Bodies... [H]e plainly means, Planets of a terrestrial nature, performing their revolutions in the System of every Fix'd Star.”

“That saying is well known, so often used by Anaxagoras, and his Scholars, Achelaus and Euripides, Namely, "That the Sun and Stars were fiery or red-hot Stones and Golden Clods." Of the same mind also were Democritus, Metrodorus, and Diogenes...”

“[I]f we look back to the first Rise of Astronomy... we shall find nothing better approv'd of, nothing more universally entertained among the several Sects of Philosophers, than this notion of the Gravity of the Celestial Bodies.”

“[W]e do still tread in the steps of the Ancients in this Physical Astronomy; inasmuch as they knew that the Celestial Bodies gravitated towards each other, and were retain'd in their Orbits by the force of Gravity; and were also apprized of the Law of this Gravity.”

“[T]he Physics delivered in the following Work... was both known and diligently cultivated by the most ancient Philosophers. ...[T]he true System of the World, approv'd of Pythagoras, and others among the Ancients...”