1. Our argument is found in D. Topper and D.E. Vincent, “An Analysis of Newton’s Projectile Diagram,” European Journal of Physics,20 (1999), pp. 59–66. The critique is Michael Nauenberg, “Comment on ‘An Analysis of Newton’s Projectile Diagram,”’ European Journal of Physics, 21 (2000), pp. L5–L6. Our rejoinder is D. Topper and D.E. Vincent, “Reply to Comment on ‘An Analysis of Newton’s Projectile Diagram,”’ European Journal of Physics, 21 (2000), pp. L7–L8.
2. Philip and Phylis Morrison, The Ring of Truth: An Inquiry into How We Know What We Know (New York: Random House, 1987), Newton’s sketch is on p. 250.
3. Isaac Newton, De Mundi Systemate (A Treatise on the System of the World), English trans. (London: Dawsons, 1969). The most recent translation (of the third edition) of the Prin-cipiais Isaac Newton, The Principia: Mathematical Principles of Natural Philosophy, I. Bernard Cohen and Anne Whitman, trans. (Berkeley and Los Angeles: University of California Press, 1999). I was able to reconstruct the history of various versions of the projectile passage using Isaac Newton’s “Philosophiae Naturalis Principia Mathematica,” 2 vols., Alexandre Koyrè and I. Bernard Cohen, eds. (Cambridge, MA: Harvard University Press, 1972).
4. On Henry Cavendish, see Christa Jungnickel and Russell McCormmach, Cavendish: The Experimental Life (Cranbury, NJ: Bucknell University Press, rev. ed., 1999), pp. 440–456, and B.E. Clotfelter, “The Cavendish Experiment as Cavendish Knew It,” American Journal of Physics, 55 (March, 1987), pp. 210–213.
5. Three historical books that I found to contain the erroneous spiral: T.S. Kuhn, The Coper-nican Revolution: Planetary Astronomy in the Development of Western Thought (Cam-bridge, MA: Harvard University Press, 1985); S. Toulmin and J. Goodfield, The Fabric of the Heavens: The Development of Astronomy and Dynamics (New York: Harper Torchbook, 1961); and A. Koestler, The Sleepwalkers: A History of Man’s Changing Vision of the Universe (Harmondsworth: Penguin, 1964).