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Published online by Cambridge University Press: 13 April 2010
Three hundred and forty-one years ago, on Saturday September 19, 1648, at eight a.m., Blaise Pascal's Great Experiment took place. Following Pascal's explicit instructions, his brother-in-law Florin Périer took two identical glass tubes and filled them with mercury. He inverted the tubes and submerged the open end in a bowl containing an inch of mercury. Thus he set up two Torricellian baroscopes in the garden of the Minim Monastery, at the base of the Puy-de-Dôme, one of the highest mountains in central France. The height of the mercury in each tube was carefully measured and marked on the glass. The measurements, which were identical, were recorded. One device was left in place, as a control baroscope, with an observer. The other was dismantled.
1 This exercise is often called “Torricelli's experiment”, but this is a misnomer. Torricelli had simply constructed the first baroscope—a device for observing the effects of atmospheric pressure, but not for recording or measuring it. The barometer was invented when Pascal affixed a measure to the inverted glass tube. At best, this procedure could be called an “adventure” in Ian Hacking's terminology; for Torricelli had no theory. He wanted to see what would happen in the tube, when a liquid fourteen times heavier than water was used. The hypothesis-testing and experimentation came later. See Hacking, Ian, The Emergence of Probability (London: Cambridge University Press, 1975), chap. 6.Google Scholar
2 Pascal, Blaise, “Lettre de M. Périer à M. Pascal le Jeune, du 22 Septembre 1648”, 351–358Google Scholar, in Oeuvres, vol. 2. All references to Pascal's work are to the Brunschvicg, Boutroux and Gazier edition: Oeuvres de Blaise Pascal, vols. 1–14 (Paris: Hachette [1904–1914], reprinted 1965Google Scholar). I also use Louis Lafuma's edition: Pascal: Oeuvres complètes (Paris: Editions du Seuil, 1963)Google Scholar. Cailliet, Emile's Great Shorter Works of Pascal (Philadelphia, PA: Westminster Press, 1948)Google Scholar contains the best translation of the major scientific works.
3 See Encyclopedia Britannica, vol. 3 (Toronto: Encyclopaedia Britannica Ltd., 1955), 128–129.Google Scholar
4 Pascal, , Expériences nouvelles touchant le vide, 54–76Google Scholar; Préface sur le traitéd du vide, 129–145Google Scholar; “Réponse de Blaise Pascal au très révérend père Noël”, 90–106Google Scholar; “Lettre à M. Le Pailleur, au sujet du père Noël”, 179–211, Oeuvres, vol. 2.Google Scholar
5 Pascal, , “Lettre à M. Périer”, 154, in Oeuvres, vol. 2Google Scholar; Cailliet, , Shorter Works, 56, in Oeuvres, vol. 2.Google Scholar
6 Pascal, , Oeuvres, vol. 2, 160Google Scholar. The nomenclature of the theorem is Desargues', not Pascal's (see Oeuvres, vol. 1, 248).Google Scholar
7 Pascal, , Oeuvres, vol. 2, 152 and 161.Google Scholar
8 Ibid., 160–161.
9 Ibid., 165–167. At the famous series of meetings between Descartes and Pascal in September 1647, Mersenne's idea of ascending a mountain was discussed, and Pascal's famous experiment involving a vacuum-within-a-vacuum was demonstrated. Since setting controls and testing the null hypothesis was part of Pascal's own methodology and philosophy of science, the actual experimental design could not have been suggested by Descartes.
10 Boyle, Robert, Nova Experimenta de Aëre, 22 and 93Google Scholar, cited in Pascal, , Oeuvres, vol. 2, 281.Google Scholar
11 Pascal, , Oeuvres, vol. 2, 162.Google Scholar
12 Pascal, , “Lettre à M. Périer”, 161–162Google Scholar; Cailliet, , Shorter Works, 58.Google Scholar
13 Wolf, A., A History of Science, Technology, and Philosophy in the 16th and 17th Centuries (London: George Allen & Unwin, 1950)Google Scholar. See also Hall, A. R., “The Scientific Movement”, in The New Cambridge Modern History, vol. 5, 47–48Google Scholar; The Ascendancy of France, 1648–1688, edited by Carsten, F. L. (London: Cambridge University Press, 1961), chap. 3, 47–72.Google Scholar
14 See most modern logic texts with chapters on Science and Hypotheses, e.g., Carney, James D. and Scheer, Richard K., Logic (New York: Macmillan, 1980), 350Google Scholar. Or see Hurley, Patrick J., A Concise Introduction to Logic (Belmont, CA: Wadsworth, 1985), 445–447.Google Scholar
15 Boyer, Timothy H., “The Classical Vacuum”, Scientific American (August 1985), 70–71.Google Scholar
16 See, e.g., Nozick, Robert, Philosophical Explanations (Cambridge, MA: Harvard University Press, 1981), 251Google Scholar. “Experimental science is a testing of hypotheses, manipulating conditions (and controlling other variables) so that (certain) subjunctives (or their probabilistic variants) hold true; artificial conditions are created so as to connect a particular hypothesis H with observable data by (those) subjunctive evidential relations.”
17 On tracking and reliability, see Nozick, , Philosophical Explanations, 178–179 and 264–268Google Scholar. For Pascal's discussions of reliability, see “Réponse de Pascal au très bon révérend père Noël”, 100–101Google Scholar; Préface surle traité du vide, 136Google Scholar; “Lettrede Pascal à M. Périer”, 159 and 162Google Scholar; Récit de la Grande Expérience des Liqueurs, 371–372Google Scholar, all in Oeuvres, vol. 2.
18 Pascal, , “De l'Art de Persuader”, 287–288Google Scholar, Oeuvres, vol. 9; Cailliet, , Shorter Works, 210Google Scholar. For Pascal's discussions of truth, see also Préface sur le traité du vide, 136–137Google Scholar; “Reponse de Blaise Pascal au très révérend père Noël”, 90–106Google Scholar; “Lettre à M. le Pailleur”, 179–211Google Scholar, all in Oeuvres, vol. 2.
19 Pascal, , Oeuvres, vol. 2, 132Google Scholar; Cailliet, , Shorter Works, 52.Google Scholar
20 Pascal, , Oeuvres, vol. 2, 136Google Scholar; Cailliet, , Shorter Works, 53.Google Scholar
21 Lafurna, , Pascal, 641.Google Scholar
22 Ibid., 641.
23 I borrow this way of setting out experimental design from Drickamer, L. C. and Vessey, S. H., Animal Behavior: Concepts, Processes, and Methods (Boston, MA: Prindle, Weber and Schmidt, 1985), chap. 3, 41–49Google Scholar. Their hypothesis involves aggressive behaviour in the male of the species. On the toxicity of metallic mercury, see Putman, J. J. and Madden, R. W., “Quicksilver and Slow Death”, National Geographic (Washington, October 1972), 507–527.Google Scholar
24 On the null and alternative hypotheses, see Drickamer, and Vessey, , Animal Behavior, 42Google Scholar. See also Dyckman, Thomas R. and Thomas, L. Joseph, Fundamental Statistics for Business and Economics (Englewood Cliffs, NJ: Prentice Hall, 1977), 369–370.Google Scholar
25 On the importance of experimental design, see also Laudan, Larry, “Explaining the Success of Science”, in Science and Reality, ed. Cushing, J. T. et al. (Notre Dame, IN: University of Notre Dame Press, 1984), 83–105.Google Scholar
26 Lafuma, , Pascal, 194–221.Google Scholar
27 Pascal, , Oeuvres, vol. 2, 160.Google Scholar
28 Ibid., 160; Cailliet, , Shorter Works, 57–58.Google Scholar
29 Pascal, , “Lettre de M. Périer”, 353Google Scholar, in Oeuvres, vol. 2: “Firstly I poured into a container sixteen lbs. of quicksilver which I had rectified for three days prior to the experiment.”
30 Ibid., 352. Mosnier's account was sent to Des Noyers, who sent it to Gassendi (see 359–361).
31 An explanation of the Paris and Macon systems of measurement is to be found in Humbert, Pierre's L'Oeuvre scientifique de Blaise Pascal (Paris: Editions Albin Michel, 1947)Google Scholar. On the importance of independent data points, see Drickamer, and Bessey, , Animal Behavior, 44–46.Google Scholar
32 For the statistical tables, see Pascal, , Fragments du traite du vide, 524–529, in Oeuvres, vol. 2.Google Scholar
33 Ibid., 353–354 and 357.
34 Ibid., 367 and 369–370. Cailliet, , Shorter WorksGoogle Scholar, unfortunately does not contain a translation of Pascal's Account of the Great Experiment.
35 Laudan, , “Success of Science”, 101.Google Scholar
36 Pascal, , Traité de la pesanteur de la masse de l'air, 200–201, in Oeuvres, vol. 3Google Scholar. Gassendi and Boyle thought this balloon experiment even more decisive than the Puy-de-Dôme one.
37 Pascal's invention of the siphon-barometer is cited in the fragments of the Traite du vide. In this work, which dates from early 1651, Pascal mentions these barometers as having been used earlier by him. See Pascal, , Oeuvres, vol. 2, 543–544Google Scholar. Boyle's Law is in the second edition of his New Experiments Touching the Spring of the Air. There, Boyle wrote: “This observation does both very well agree with and confirm our hypothesis [which was Boyle's Law], and will be easily discerned by him, that takes notice that we teach, and Monsieur Pascall [sic] and our English friends' experiments prove, that the greater the weight is that leans upon the air, the more forcible is the endeavour of dilatation ….”
38 For a similar conclusion about the cause of Pascal's illness and subsequent death, see Katharine, and Montague, Peter, Mercury (New York: Sierra Club, 1971).Google Scholar
