MOON SUPERSTITIONS.
(Vol. viii., pp. 79. 145.)
Notwithstanding the authority upon which Mr. Ingleby founds the assertion, that there is not the "slightest observable dependence" between the moon and the weather, the dictum is open to something more than doubt. That the popular belief of a full moon bringing fine weather is not strictly correct, is undoubted; and the majority of the popular ideas entertained on the influence of the moon on the weather are equally fallacious; but that the moon exerts no influence whatever on the changes of the weather, is a statement involving grave errors.
The action of the moon on meteorological processes is a highly complex problem; but the principal conclusions to which scientific observations tend, on this matter, may be pointed out without perhaps encroaching too much on the space of "N. & Q."
Luke Howard, of Ackworth, several years ago, concluded, from a series of elaborate observations, extending over many years, that the moon exerted a distinct influence on atmospheric pressure: and Col. Sabine has more recently shown, from observations made at the British Magnetical and Meteorological Observatory at St. Helena since 1842—
"That the attraction of the moon causes the mercury in the barometer to stand, on the average, .004 of an English inch higher when the moon is on the meridian above or below the pole, than when she is six hours distant from the meridian."—Cosmos, vol. i. note 381, (author. trans.); Phil. Trans., 1847, art. v.
Luke Howard farther gives cogent reasons, from his tabulated observations, for the conclusion that the moon has an appreciable effect upon the weather, exerted through the influence of its attraction on the course and direction of the winds, upon which it acts as a marked disturbing cause; and through them it affects the local distribution of temperature, and the density of the atmosphere. There is no constant agreement between the phases of the moon and certain states of the weather; but an apparent connexion is not unfrequently observed, due to the prevalence of certain winds, which would satisfactorily account for the origin and persistence of the popular belief: for, "it is the peculiar and perpetual error of the human understanding to be more moved and excited by affirmatives than negatives" (Nov. Org., Aph. 46.). For example, in 1807, "not a twentieth part of the rain of the year fell in that quarter of the whole space, which occurred under the influence of the moon at full" (Lectures on Meteorology, by L. Howard, 1837, p. 81.). In 1808, however, this phase lost this character completely.
A more marked relation is found between the state of the weather and the declination of the moon: for—
"It would appear, that while the moon is far south of the equator, there falls but a moderate quantity of rain with us; that while she is crossing the equator towards these latitudes, our rain increases; that the greatest depth of rain falls, with us, in the week in which she is in the full north declination, or most nearly vertical to these latitudes; and that during her return over the equator to the south, the rain is reduced to its minimum quantity. And this distribution obtains in very nearly the same proportions both in an extremely dry and in an extremely wet season."—Climate of London, by L. Howard, vol. ii. p. 251., 1820.