from the distribution at other levels. The 

 standard depths, in meters below the sea sur- 

 face are: 0, 10, 20, 30, 50, 75, 100, 150, 200, 

 (250), 300, 400, 500, 600, (700), 800, 1,000, 

 1,200, 1,500, 2,000, 2,500, 3,000, 4,000, and 

 thence every 1,000-meter interval to the bottom. 

 The depths in parentheses are optional. All 

 data obtained by Nansen bottles and used at 

 the Hydrographic Office are adjusted to the 

 standard depths. The optional 250-meter 

 depth is included but the 700-meter depth 

 may be omitted. 



2-12 Spacing (he Nansen Bottles. — Several 

 factors influence the spacing of Nansen bottles 

 along the wire and vary from station to station 

 with the types of data sought. While it is 

 desired to obtain data at or near standard 

 depths, this is accomplished only under condi- 

 tions of zero or near zero wire angles. Such 

 conditions are relatively rare at sea. Iso- 

 conditions of temperature, salinity, etc., may 

 warrant wider spacing of bottles. Steep tem- 

 perature, salinity, and oxygen gradients may 

 require closer spacing in order to better de- 

 lineate them. 



2-13 Placing the Nansen Bottle on the 

 Wire. — After the oceanographic winch has been 

 tested and the lead weight shackled to the wire 

 and lowered over the side, it usually is run 

 down to about 10 or 15 meters below the water- 

 line and the winch stopped. This holds the 

 lead clear of the hull and the wire steady 

 against the roll of the ship. After the meter 

 dials are set at zero, the first Nansen bottle 

 can be placed on the wire. It should be noted 

 that the Nansen bottle to be placed first on the 

 wire is the one that will go to greatest depth, etc. 

 Clamp the bottle to the wire and securely tighten 

 the wing nut on the clamp. Release the locking 

 spring from the connecting rod and swing the 

 bottle up. This opens the valves at each end of 

 tlie bottle and reverses the thermometers. De- 

 press the messenger trigger of the tripping as- 

 sembly on the upper end of the bottle and fasten 

 it to the wire. NIake sure that the messenger 

 trigger returns to the "up" position and the pin 

 holding the bottle to the wire has returned com- 

 pletely to the closed position. Next check to 

 insure that the drain petcock, now at the upper 

 end, and the air vent, now at the lower end, are 

 both closed. This is important. Check the 

 reversing thermometers to insure that they 

 have reversed properly and that the mercury 

 has drained out of the bulb into the reservoir. 

 Occasionally, the mercury will stick in the bulb 

 and not drain readily. Tapping the glass with 

 the fingers usually will release the mercury 

 from the bulb and permit it to drain. In more 



stubborn cases, the thermometer may have to 

 be removed and the methods given in the ap- 

 pendix may be applied. It is most important 

 to see that the mercury has properly drained 

 before lowering the Nansen bottle. To all 

 bottles except the first bottle placed on the 

 wire, a messenger must be attached. Each 

 messenger has a length of wire about 6 or 8 

 inches long, with a small eye in the outer end. 

 This eye is attached to the Nansen bottle by 

 inserting it into the small slot in the under side 

 of the clamp assembly. Depress the release 

 arm, insert the eye, and release the arm. Make 

 sure the messenger release pin has seated itself 

 through the eye. Attach the messenger to 

 the wire below the bottle. The bottle is now 

 ready for lowering. 



2-14 Lowering the Nansen Bottle. — ^Lower 

 the Nansen bottle slowly until it has entered 

 the water and the air has been expelled. After 

 the bottle has reached a couple of meters below 

 the surface gradually increase the speed of the 

 winch to its normal lowering speed. If the 

 bottle is lowered too rapidly, the messenger 

 may be released prematurely or the bottle may 

 trip as it enters the water. In the first instance, 

 any bottles below will be tripped, and in the 

 second the bottle will be crushed if any air 

 should be trapped in it and the lowering con- 

 tinued. After the last bottle has been lowered 

 to its indicated depth, plus the distance from 

 the platform to the surface, the winch is 

 stopped (fig. 2-3). Record this time on ocean- 

 ographic log sheet A as indicated in chapter 14. 



2-15 Measuring the Wire Angle and Drop- 

 ping the Messenger. — Before the wire angle is 

 measured and the messenger dropped to trip 

 the first bottle, a certain amount of time must 

 be allowed to permit the reversing thermometers 

 to come to the exact temperature of the water 

 and to let the Nansen bottles flush. The 

 Nansen bottles, having small valve openings, 

 tend to retain a portion of higher level water 

 as they are lowered. They must therefore sit 

 in the lowered position a certain time to permit 

 this residue to flush and be replaced by water 

 in situ. A minimum of 6 minutes is considered 

 necessary to bring the thermometers to temper- 

 ature and let the bottles properly flush. 



The time required for a Nansen bottle mes- 

 senger to drop may be figured at 200 meters 

 per minute for wire angles less than 35° and 

 at 150 meters per minute for wire angles greater 

 than 35°. 



Some time can be saved when deep casts 

 are down by deducting messenger dropping 

 time for the distance to the shallowest bottle 

 from the 6 minutes required for the bottles to 



H. O. 607 



11 



