If this data confuses bear in mind the simple ordinary progress of the barometer in the usual storm: First, it will stand steady for a day or so at any point between 30.10 and 30.50. Then the glass will begin (for most storms) to fall gradually. As the center nears the fall hastens. After the lowest point has been reached a slight rise will be followed by another slight fall and then the final long rise will commence. The rain begins and ceases at different stages for different storms, depending upon the wind's velocity and direction. For every 900 feet of altitude the height of the mercury is about one inch less. Do not complain that your barometer is inaccurate if you are living up in the mountains and your readings are not the same as the weather reports which are reduced to sea level. All the figures given in this chapter are for sea level and if your house is 1900 feet above you must move the copper hand of your aneroid 1.95 inches from the pressure hand. If the pressure hand would read 28.05 the adjustable copper hand would read 30.00 which is the sea level reading. 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.