The Eclipse of the Sun: Sun-dials, Clocks and Natural Time in the Late Seventeenth Century


In: Early Science and Medicine

The Sun, in the early seventeenth century was, as it always had been, the ultimate arbiter of time-measurement. In the last quarter of the century however this role was called into question as the new precision of post-Huygenian clocks revealed that natural time and the artificial mean time of the clock were not the same. Initially the question was little understood by the general public. The paper examines some early attempts to explain why “Sun-time” in 1700 was no longer “true-time.”


  • 13

    Nelson to Oldenburg, 15 December 1670, ibid.7: 324.

  • 14

    Nelson to Oldenburg, 15 December 1670, ibid.7: 324.

  • 30

    Flamsteed to Newton 7 February 1694/5, Correspondence, 83.

  • 40

    Augarde, Ouvriers, 73, 387–88. Raillard’s critique of Sully is apparently lost. The Equation manuscript is in a private collection. In 1740 Raillard supplied similar, but revised, tables to Antoine Thiout for publication in his Traité de l’horlogerie, méchanique et pratique …, 2 vols (Paris, 1741), 291–94.

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  • 52

    The passage to which Nelson here refers, pp. 62–63, runs, “In giving the reason or cause [of the inequality of time] there is great difference, some make the reason of it to be the obliquity of the Zodiack, wherein the Sun moveth; others make the difference between the Suns true longitude, and his right ascention to be the absolute cause; others make the unequal motion of the Sun in the Zodiack to be the cause (which I incline to) but the cause of this cause, I suppose, all are ignorant of, because God in his word never revealed it, and for any other way of knowing it, I suppose, ’tis so far from our attainment that the wisdome of the best Astronomer will in this prove but foolishness however they may otherwise pretend.”

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