Figure il-3. A meter wheel reading of a Naiisen bottle 

 east. 



remain in situ. For example, it takes 3 minutes 

 for a messenger to reach and trip a bottle at 

 600 meters. Therefore, the messenger may be 

 dropped 3 minutes after the cast is down 

 instead of waiting the full 6 minutes before 

 dropping it. 



Measure the wire angle with the wire angle 

 indicator. Take an average of several readings 

 to allow for the roll of the ship. Do this 

 before dropping the messenger (fig. 2-4). 



2-16 Bringing the Nansen Bottle In. — 

 After sufficient time has been allowed for the 

 lowest bottle to be tripped, start the winch and 

 commence hoisting. Keep a sharp lookout for 

 the first bottle. Inform the winch operator 

 when the bottle is in sight and again when at 

 the surface of the water. Then, carefully hoist 

 the bottle to the platform. Remove the mes- 

 senger from the wire above the bottle. Un- 

 clamp the Nansen bottle from the wire and 

 return it to the rack, being very careful to keep 

 the bottle always in a vertical position with the 

 clamp assembly at the top. This will prevent 

 accidental reversing of the thermometers. 



When all the Nansen bottles have been 

 returned to the rack, the water samples are 

 drawn. The methods used for drawing samples 

 are given in sections 2-28 and 2-41. After 



Figure 2-4. Deteriuining the wire angle of a Nansen 

 bottle cast. 



all water samples have been drawn, drain the 

 excess water from the Nansen bottles. 



Time is allowed for the reversing ther- 

 mometers to come to air temperature before 

 they are read. This usually takes from 10 to 

 15 minutes depending upon air conditions and 

 may be checked by observing the Auxiliary 

 thermometers. When all Auxiliary thermom- 

 eters, in both the protected and unprotected 

 cases, read approximately the same they can 

 be presumed to have come to air temperature. 

 The Main and Auxiliary thermometers in each 

 case are read and the data recorded on ocea- 

 nographic log sheet A as described in chapter 14 

 (fig. 2-5). 



2-17 USE OF DEEP-SEA REVERSING 

 THERMOMETERS.— Deep-sea reversing ther- 

 mometers are delicate, but highly accurate, 

 mercurial thermometers specially designed for 

 recording water temperatures in situ by being 

 reversed when the Nansen bottle is tripped by 

 the messenger. There are two types of revers- 

 ing thermometers, protected and unprotected. 

 The temperature scale is Celsius (centigrade) 

 and is carefully etched on the glass stem. Each 

 thermometer used by the Hydrographic Office 

 is calibrated by the Bureau of Standards before 

 it is used at sea. The scale is read with a ther- 



12 



H. O. 607 



