Figure E-8. Drawing water samples. 



about one- fourth full. Thoroughly rinse the bot- 

 tle by shaking vigorously and pour the rinse 

 water over the screw cap. Rinse at least twice. 

 When the bottle is rinsed, open the petcock, fill 

 the bottle to about 1 mch from the top, and 

 close the petcock. Cap the bottle and replace in 

 rack. If the nutrient sample is to be analyzed 

 at a later date, it should be quick frozen within 

 30 minutes. 



Step 9. Drawing the Salinity Sample. — After 

 the oxygen and nutrient samples are drawn, 

 draw the salinity samples. Use a clean citrate of 

 magnesia bottle with a well seated stopper and 

 washer. Open the petcock (the delivery tube is 

 not needed) and fill the bottle about one- fourth 

 full. Thoroughly rinse the bottle by shaking 

 vigorously and pouring the rinse water over 

 the stopper and the rubber washer. Rinse at 

 least twice. When the bottle is rinsed, open the 

 petcock, fill the bottle to within 1 inch of the 

 top, and close the petcock. A 1-inch air space 

 must be left to allow for expansion. Seal the 

 bottle and return to the rack. 



Step 10. Checking Water Sample Bottle Num- 

 bers and A-Sheet. — After the water samples 

 are drawn, check to make certain that the num- 



bers on the water sample bottles are legible, 

 that they agree with A-Sheet entries, and that 

 they have been drawn from the Nansen bottles 

 indicated on the A-Sheet. Move samples to the 

 laboratory for analysis or storage. 



Step 11. Reading and Recording Tempera- 

 tures. — After the cast is in and the water sam- 

 ples are drawn, allow time for the reversing 

 thermometers to come to air temperature be- 

 fore reading temperatures. This usually takes 

 from 10 to 15 minutes. For optimum results, 

 the ship should remain on station until ther- 

 mometers are read. When all auxiliary ther- 

 mometers in both the protected and miprotected 

 thermometers read approximately the same, the 

 thermometers can be presumed to have come to 

 air temperature. 



A special thermometer viewer, with a 6-X 

 lens mounted in a brass tube, is used for read- 

 ing the thermometers (fig. E-9). The front end 

 of the tube has two V notches for alining the 

 viewer against the glass jacket of the thermom- 

 eter. In addition, a flashlight may be required 

 when reading the thermometers. Exercise care 

 in reading the position of the mercury column 

 (fig. E-10) . If the ship is rolling and the mer- 

 cury columii is fluctuating, read at "midroll." 

 Two persons are required for reading and re- 

 cording temperatures (fig. E-11). Observer 

 number one reads all thermometers while num- 

 ber two records ; then, they change, and number 

 two reads wliile number one records. The main 



Figure E-0. Reading the reversing thermometer with 

 viewer. 



E^ 



