1. See G. E. R. Lloyd， Proceedings of the Cambridge Philosophical Society， N.S. 10， 50 （1972）， reprinted in Methods and Problems in Greek Science （Cambridge University Press， Cambridge， 1991）。
2. Galileo Galilei， Two New Sciences， trans. Stillman Drake （University of Wisconsin Press， Madison， 1974）， p. 68.
3. Stillman Drake， Galileo （Oxford University Press， Oxford， 1980）， p. 33.
4. T. B. Settle， “An Experiment in the History of Science，” Science 133， 19 （1961）。
5. This is Drake’s conclusion in the endnote to p. 259 of Galileo Galilei， Dialogue Concerning the Two Chief World Systems： Ptolemaic and Copernican， trans. Stillman Drake （Modern Library， New York， 2001）。
6. Our knowledge of this experiment is based on an unpublished document， folio 116v， in Biblioteca Nazionale Centrale， Florence. See Stillman Drake， Galileo at Work—His Scientific Biography （University of Chicago Press， Chicago， Ill.， 1978）， pp. 128–32; A. J. Hahn， “The Pendulum Swings Again： A Mathematical Reassessment of Galileo’s Experiments with Inclined Planes，” Archive for the History of the Exact Sciences 56， 339 （2002）， with a reproduction of the folio on p. 344.
7. Carlo M. Cipolla， Clocks and Culture 1300–1700 （W. W. Norton， New York， 1978）， pp. 59， 138.
8. Christiaan Huygens， The Pendulum Clock or Geometrical Demonstrations Concerning the Motion of Pendula as Applied to Clocks， trans. Richard J. Blackwell （Iowa State University Press， Ames， 1986）， p. 171.
9. This measurement was described in detail by Alexandre Koyré in Proceedings of the American Philosophical Society 97， 222 （1953） and 45， 329 （1955）。 Also see Christopher M. Graney， “Anatomy of a Fall： Giovanni Battista Riccioli and the Story of g，” Physics Today， September 2012， pp. 36–40.
10. On the controversy over these conservation laws， see G. E. Smith， “The Vis-Viva Dispute： A Controversy at the Dawn of Mathematics，” Physics Today， October 2006， p. 31.
11. Christiaan Huygens， Treatise on Light， trans. Silvanus P. Thompson （University of Chicago Press， Chicago， Ill.， 1945）， p. vi.
12. Quoted by Steven Shapin in The Scientific Revolution （University of Chicago Press， Chicago， Ill.， 1996）， p. 105.
13. Ibid.， p. 185.
