One good thing to remember is that a barometer falls lower for high winds than for heavy rain. A fall of two- or three-tenths of an inch in four hours brings a gale. In the ordinary gale the wind blows hardest when the barometer begins its rise from a very low point.
In summer a suddenly falling barometer foretells a thunderstorm, and if the corresponding rise does not at once take place the unsettled conditions will continue with probably another thunderstorm. If you see the thunderstorm first, that is, if the barometer is not affected by the approaching black cloud you may be sure that the storm will amount to nothing.
The man in the fields or along the shore has many natural barometers in animal life. But these natural barometers only corroborate; they do not foretell, at least very long before. Some are useful at times and among these the birds are foremost. The observant Zuñis have incorporated this in one of their pretty proverbs, “When chimney swallows circle and call they speak of rain.” As a matter of fact the swallows are circling most of the time after insects. If they are flying high it is because the bugs are flying high and that is because there is no danger of rain. As the rain nears the air gets moister, the bugs and the birds fly lower.
Whether they do this because their instinct is to avoid a wetting or because the lighter atmosphere of a cyclone makes flying more difficult, particularly at altitudes, I do not know. For weather purposes it is enough to watch their comparative levels. Wild geese are excellent signs, I am told, but it would be a dry country that waits for a sight of them for its rain.
Bees localize before a storm and will not swarm. Flies crowd upon the screens of houses when humidity is high, possibly because the appetizing odors from within are buoyed afar by the heavy air. Cuckoos seek the higher ground in fair weather and disappear into bottom lands before a rain. Although they are called rain-crows they are heard in all weathers.
Smoke is as good an evidence of barometric pressure as anything except the instrument itself. On clear, still days it will mount; on humid days without wind it will cling to the hill. There is that difference. But it takes skill and many comparisons to gauge its angles in the wind. It becomes a test in observation and finally rewards one by becoming an excellent sign not only of air texture but of the direction of its currents.
No reference to barometers would be complete without mentioning spiders. They show a most delicate apprehension of changing conditions. If the day is to be fine and without wind they will run out long threads and be rather active. If the rain is nearing they strengthen their webs, shorten the filaments and sit dully in the center. Fresh webs on the lawn insure a clear day. But for the commuter, whose time is money, there is little leisure to consider the spider.
As a natural result of the variation in altitude affecting the barometer the words which are printed on the face become entirely useless. In some places it would be impossible for the needle to point higher than “Very Stormy.” Even at sea level a sudden fall to “Fair” would cause a rain, much to the indignation of the person who thought that he had purchased a self-registering weather prophet. Disregard the words but watch the needle and you will never be surprised at what the weather is doing next.