Page:Popular Science Monthly Volume 32.djvu/501

Rh of the Canadian Meteorological Department, once told me that be had very frequently noticed a tendency in the weather to change and repeat itself every seven days. A similar seven-day periodicity has been observed in the United States. The meteorological conditions of a large continent, it must be remembered, are simpler than those of our own little islands, and hence it is possible that a cycle almost completely masked here might disclose itself there. It is not to be supposed that I am contending for a cycle due to the moon. I only wish to point out that there is some evidence of the existence of a seven-day weather period, which may sometimes happen to be coincident with the lunar phases; and if this be really so, it is not at all wonderful that our forefathers were led to infer a connection, or that even "educated people" continue to put a certain amount of faith in a rule so well founded.

But pre-eminently the lunar cycle is that of eighteen and a half years—the ancient Saros, or period of revolution of the lunar node. It has been traced in sundry phenomena, including the amount of rainfall and the recurrence of epidemic pestilences. The evidence, of course, is extremely shaky, though scarcely more so than much of that adduced in favor of the sun-spot cycle. The truth seems to be that in certain lines of inquiry, if an investigator starts with a predetermined system of any kind, statistics will bear him out, or can be made to bear him out.

In closing this hasty survey of a branch of mixed knowledge and ignorance, science combined with superstition, I would repeat the observation with which I set out (and which I have now in a measure justified), that it is unfair to stigmatize the whole moon-and-the-weather theme as unworthy of serious treatment—as a mere surviving fragment of astrology. There is a great deal of nonsense in it, more nonsense than sense; and if the two must sink or swim together, it would be better to let the sense go than to preserve both. But why should they be inseparable? We have sifted a little grain out of much chaff before now; and there is this great gain in the result, that the sifted chaff is chaff, obviously, demonstrably, and can not lay claim to a spurious value in the eyes of the short-sighted by the admixture of a proportion of the valued thing. There are weather wiseacres who know that there is truth in some of their cherished lunar proverbs; and the unconditional repudiation of every saying with moon in it by men of science simply convinces these old fellows that the men of science do not understand what they are talking about, and makes them cling all the more vigorously to their ill-used beliefs. If we were to set about it in a different way, and to accept the sayings that science can sanction, and only repudiate the rest, we would have a better chance of success in combating this irrepressible error. For it is the truth in the error that makes it irrepressible.—Longman's Magazine.