Note 35 — Chapter VII · Special Methods of Induction applicable to Quantity.

This period of nineteen years was also selected for a reason which is alluded to in a former note. It was thought that this period secured the inquirer from the errours which might be produced by the partial coincidence of the Arguments of different irregularities; for example, those due to the moon’s Parallax and to the moon’s Declination. It has since been found (Phil. Tr. 1838. On the Determination of the Laws of the Tides from Short Series of Observations), that with regard to Parallax at least, the Means of one year give sufficient accuracy.