PRESSURE 



53 



6233.2. Enter across the top of the chart the date and position of each 

 day's record in appropriate spaces on the 1200 (Noon) line. 



6233.3. All time entries should be in Greenwich Meridian Time. 



6233.4. When the pen has been reset (see JI6221) to compensate for a 

 large pressure change, indicate and check the points of change to be cer- 

 tain that the pen was reset to its normal position following return to normal 

 pressure. 



6234. Marine barograph. Weather Bureau Model G-222 is similar to 

 Weather Bureau Model G-220, however, it differs somewhat in construction. 

 Model G-222, due to its improved inherent balance is more adaptable for 

 shipboard use. It is contained in an airtight case with two vent holes in 

 the base, one a plug and the other a hose connection. These vents provide 

 a convenient means of connecting the barograph to a static head exposed 

 to outside air pressure when necessary. 



6234.1. Static Charge on Marine Barograph. The window of the Model 

 G-222 marine barograph is made of plastic and when cleaned with a dry cloth 

 develops a static charge. If the air is dry the static charge does not dissi- 

 pate and may become strong enough to pull the pen off the chart. Damage 

 may result if the covering case is removed when the pen arm is held against 

 the window by the static charge. Wiping the barograph case with a damp 

 cloth will provide sufficient conductivity to bleed off the static charge, how- 

 ever, a more lasting effect can be gained by rubbing a few drops of liquid 

 detergent, or a small amount of powdered graphite on the window. 



^' 



Figure 8. --Barograph, Marine, W. B. Model G-222 



