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 well; neither the one nor the other was possessed of a daily weather map. The wind was a fair barometer; the blinking of the stars was an excellent hygrometer. The discovery of the underlying principles of barometric pressure was the beginning of modern meteorology. The use of the barometer quickly appealed to sailors, and practically every deep-water vessel in the world is equipped with one. Transportation companies, lighting companies, farmers and manufacturers find it a necessity. The invention of the aneroid barometer has popularized its use tremendously.

In the hands of one without experience, or without training in the use of it, the barometer is usually a disappointment. To the trained observer, or to the observer who has gained wisdom by experience, it is an instrument of the highest value. To be serviceable in forecasting weather conditions it must be watched—not casually but systematically. The experience that comes from intelligent study of pressure changes will enable an observer to command most gratifying results.

General Pressure Indications.—As a rule, pressure changes should not be considered by themselves; they should be studied in conjunction with changes in temperature, humidity and wind direction. There are, however, certain general weather conditions indicated by changes in barometric pressure which hold good: