(GMT) the hoisting commenced in the VP 

 cohimn. Post a lookout during the entire re- 

 trieval operation. The lookout should signal the 

 winch operator when the bottle is in. sight, at 

 which time the winch operator slows the winch. 

 Wiien the bottle breaks the surface, the lookout 

 again signals the winch operator, who then 

 slows the winch to a creeping speed. After care- 

 fully hoisting the bottle to the platfonn, stop 

 the winch, snap the safety line onto the bottle 

 (fig. E-7), and remove the messenger (s) and 

 bottle from the wire. Remove the safety line, 

 and keeping the bottle in a vertical position, 

 return it to its original place in the rack. 

 yOTE : Avoid excessive shock to the thermom- 

 eters. Record the meter wheel reading in the 

 VP column of the A-Sheet opposite each bottle 

 as the cast is brought in. When all Nansen 

 bottles have been returned to the rack, record 

 the time (GMT) in the IN column of the A- 

 Sheet. 



The process of transferring water from Nan- 

 sen bottles to sea water sample bottles is de- 

 scribed as "drawing water samples" (fig. E-8) ; 

 samples drawn for a certain chemical deteiTai- 

 nation are referred to as a salinity sample, 

 oxygen sample, etc. See chapter D, paragraph 

 D-14, for types of sea water sample Iwttles. 



StejD 7. Drawing the Oxygen Sample. — The 

 first sample to be drawn should be the oxygen 

 sample. Use either the amber bottle, the flask, 



or the serum bottle depending on the type 

 analysis. Loosen the air vent tliumb screw at 

 the top of the Nansen bottle. Attach a delivery 

 tube (a piece of soft- wall tygon tubing about 

 8 inches long) to the petcock. OjDen the petcock 

 and draw a small amount of water (1 inch in 

 bottle). Thoroughly rinse the bottle by swirling. 

 Rotate bottle in a horizontal position, pouring 

 the rinse water over the stopper. Rinse at least 

 twice. When bottle is rinsed, insert tip of de- 

 livery tube to the bottom of the sample bottle. 

 Open the drain petcock slowly to prevent air 

 bubbles. As the bottle fills, gradually withdraw 

 the delivery tube, always keeping the tip of the 

 tube below the surface of the sample. Allow the 

 bottle to overflow slightly, withdraw the de- 

 livery tube; then turn ofi" the petcock. Insert 

 the stopper into the mouth of the bottle in such 

 a way that no bubbles of air are trapped, and 

 allow it to seat. Invert the bottle and check for 

 presence of bubbles. If air bubbles are present 

 in the sample, discard it and draw another. 

 Oxygen samples for titration analysis must be 

 treated immediately after they have been drawn. 

 NOTE : Replicate samples are collected if anal- 

 ysis is to be by the (Micro) Winkler method. 

 Step 8. Drawing the Nutrient and Trace Metal 

 Sample. — After the oxygen sample is drawn, 

 draw nutrient and trace metal samples. Use the 

 polyethelene bottle. Open the petcock (the de- 

 livery tube is not required), and fill the bottle 



Figure E-1. Snapping the safety line onto the bottle. 



E-7 



