48 MANUAL OF MARINE METEOROLOGICAL OBSERVATIONS 



tenths, or millimeters (see Fig. 5). To insure that a precision aneroid 

 barometer will retain its calibration, it must be protected from shocks 

 or other violent motions. 



6120. READING ANEROID BAROMETERS. To determine sea- level 

 pressure from the aneroid barometer; 



6120.1. Tap the face of the instrument lightly with the finger or the eras- 

 er-end of a pencil to bring the hand to its true position. 



6120.2. Read to the nearest 0.01 inch, 0.1 millibar, or 1 millimeter, 

 estimating for values between the scale graduations. 



6120.3. Apply the correction established in accordance with J6020. 



6120.4. Example: inches 



Barometer as read 29.88 



Correction - .07 



Barometer corrected 29.81 



Figure 5. - -Aneroid barometer, W. B. Model G-101 



