29.80 or below and rising Going to Clearing and colder rapidly W A sudden fall indicates a sudden shower or high winds, or both. [Illustration: _Courtesy Julien Friez & Son Baltimore, Md._ Fig. 49 U. S. STANDARD RAIN GAUGE ] A stationary barometer indicates a continuance of existing weather conditions. (_Note_: Tap the barometer slightly on the face. If the hands move a trifle, it indicates that there is the tendency to rise or fall, depending upon the direction of movement of the hands.) Northeasterly winds precede storms that approach from the southwest; that is, in New England and the Middle States and the Ohio Valley. Southeasterly winds precede storms that approach from the Lake region. THERMOMETERS For information regarding the manufacture of thermometers, we recommend P. R. Jameson’s book, “Weather and Weather Instruments,” published by the Taylor Instrument Companies of Rochester, N. Y. Thermometers are of great importance to us in determining weather. LOCATION OF THERMOMETERS 1. They must be properly exposed. 2. A good circulation of air around them is necessary. 3. They must be properly protected from the rays of the sun. _Note_: If these instructions are not carefully followed out, errors are apt to occur, and you will be misled. For a change of wind towards northerly directions, a thermometer falls. For a change of wind toward southerly directions a thermometer rises. [Illustration: Fig. 50 GILBERT RAIN GAUGE ] MAXIMUM AND MINIMUM THERMOMETERS Maximum and minimum thermometers are used to record the daily maximum and minimum temperatures. Fig. 46 shows a typical maximum and minimum thermometer used for giving the extremes of temperature. One side of the thermometer has a scale reading, beginning at the top, from 60° below zero to 140° above zero. This is the scale used when determining the coldest temperature reached during a day. The other side of the thermometer has a scale marked from 70° below zero, beginning at the bottom and reading up, to 130° above zero. On this side the maximum heat reached during the day is recorded. There is a small metal piece in the tubes, one on each side, and as the mercury pushes ahead or recedes, the small index is left at the lowest point reached in one tube and at the highest point reached in the other. The small metal piece is drawn back to the level of the mercury by means of a small magnet. WHEN MAXIMUM TEMPERATURE IS REACHED You can generally look for maximum temperature between three and four o’clock in the afternoon. At this time the sun has reached its highest altitude. [Illustration: _Courtesy Julien Friez & Sons, Baltimore, Md._ Fig. 51 TIPPING BUCKET RAIN GAUGE ] WHEN THE MINIMUM TEMPERATURE IS REACHED