Some of these wily prophets pretend to read their predictions in the course of the planets. For this purpose, they have divided the planets into two classes, according to their positions in regard to the earth and sun: 1st, those that produce cold, and 2d, those that produce heat. By this means they pretend to prophesy how many degrees of heat or cold there will be every day at sunrise or sunset.
When critically analyzed, these prophecies prove to be theoretically and practically nothing but charlatanry.
It is beyond all doubt that the position of the planets is, to state an example, for Boston the same as for the city of Washington; if there are any heat or cold-producing planets, they would have the same effect at Boston that they would at Washington. But this is not the case. Boston has often cold weather when in Washington it is very warm, and vice versâ. Besides such a heating or cooling influence of planets would be perceivable on every spot of the earth alike which again is not warranted by facts. On the contrary it often happens that when cold winds are passing over one part of the country, warm winds are passing over another. It is almost certain that cold winters in Europe always accompany warm winters in America; and again, that cold winters in America usually accompany warm ones in Europe. On a closer examination of the facts in the case, we must conclude that, on the whole, weather-prophets take things very easy. Noting the mean heat of each day, and trusting to their good luck, they prophesy one or two degrees above or below. Now, there is no great risk in doing this, and as a matter of course such prophecies are realized one out of two. But at times, almanacs announce an extraordinary increase of cold or heat for a given day, although the situation of the planets does not change suddenly in one day. Then, their predictions very seldom prove to be correct.
In such cases the almanac-makers know how to manage affairs. The country being very large, they send for information to those places where observations on the weather are made. It is almost certain that somewhere in the land their prophesy has come true. Very likely the cold may have increased extraordinarily in the course of a day at New York, Boston, Chicago, Cincinnati, or St. Louis, etc., afterwards the weather-prophets compare their predictions with the results of observation in the various cities, and publish whatever of them are found to have been true.
CHAPTER XIII.
HAS THE MOON INFLUENCE UPON THE WEATHER?
The idea that the moon exercises an influence upon the state of the weather is very general, not only with the people, but also among the better educated. What induces them to entertain it, is not real observation of nature, but a belief which is not without a semblance of truth. If, they say, the moon has enough influence upon our waters to produce tides, it must exercise a still greater influence upon the sea of air surrounding us, and hence it must be of the greatest importance to our weather.
This is, however, an illusion. A long time ago it was proved by Laplace, that tides are caused by the great weight of a liquid. If the ocean were filled with mercury instead of water, the tides would reach a formidable height. Tides, then, do exist in the atmosphere, but in comparison much less than in the water, because the air is so much lighter. It happens that we do not live on the surface of the atmosphere, but in the lowest strata of this airy sea; and in these strata, where the weather manifests itself, the effect of the tides in the upper air is so insignificant, that nothing of it has yet been discovered in spite of most diligent barometer observations.
Learned men have had such a respect for this popular belief, that thorough observations and investigations have been made in order to settle the question.