Figure E-i. Nansen bottle being placed on wire. 



the bottle may be crushed if any air should be 

 trapped in it and the lowering continued (fig. 

 E-5). Stop the winch at each down meter wheel 

 reading, and attach the next bottle until all bot- 

 tles are on the cast. Then lower the last bottle 

 to just below the surface, stop the winch, and 

 set the brake. It is important that winch opera- 

 tions, starting and stopping, be conducted as 

 smoothly as possible to prevent pretripping of 

 bottles and malfunctioning of thermometers. 

 On the A-Sheet, record time (GMT) in DOWN 

 column, and record the meter wheel reading at 

 the top of the Down Meter Wheel Reading 

 column. On the 2d and 3d casts, after the last 

 bottle is attached, lower the cast to the wire 

 length depth of the deepest bottle plus the dis- 

 tance from the water surface to the level of at- 

 tachment by the bottle hanger. 



Step 5. Measuring the Wire Angle and Drop- 

 ping the Messenger. — Before the messenger is 

 dropped to trip the bottles on the cast, a mini- 

 mum of 10 minutes should be allowed for the 

 reversing thermometers to come to the tempera- 

 ture of the water. Measure the wire angle with 

 the wire angle indicator — a simple device for 

 measuring the angle of the oceanographic wire 

 with the vertical (fig. E-6) . Take the average of 

 several readings to allow" for roll of the ship; 

 then, drop the messenger. On the A-Sheet 

 record the wire- angle in Wire Angle (1) column 

 and the time (GMT) the messenger was 

 dropped in the MESS column. 



The time required for a Nansen bottle messen- 

 ger to reach the last bottle of the cast may be 

 computed at 200 meters per minute for wire 

 angles less than 35° and at 150 meters per min- 

 ute for wire angles greater than 35°. Time can 

 be saved when deep casts are down by deducting 

 messenger time for the distance to the shallow- 

 est bottle from the time the bottles are allowed 

 to remain /n situ. For example, if it takes 3 min- 

 utes for a messenger to reach and trip the shal- 

 lowest bottle, the messenger may be dropped 7 

 minutes after the cast is down instead of waiting 

 10 minutes. 



Step 6. Retrieving the Nansen Bottles. — After 

 sufficient time has lapsed for the deepest bottle 

 to be tripped, remeasure the wire angle, start 

 the winch, and commence hoisting. On the A- 

 Sheet, record the second wire angle measure- 

 ment in Wire Angle {£) column and the time 



Figure E-5. A crushed Nansen bottle. 



Figure E-6. Wire angle indicator. 



E-6 



