enter the sample. If any do, discard the sample 

 and begin again. Fill the sample bottle until 

 it overflows slightly and withdraw the delivery 

 tube before turning the petcock off. Insert the 

 end of the ground glass stopper into the mouth 

 of the bottle in such a way that no bubbles of 

 air are trapped, and allow it to seat. This will 

 spill a small amount of water, but will insure 

 the proper volume of sample for analysis. 



Dissolved oxygen samples must be processed 

 for analysis immediately after they have been 

 drawn. Instructions for carrying out the 

 analysis are given in chapter 13. 



2-28 Drawing Sea Water Samples for 

 Salinity Analyses. — Water samples to be an- 

 alyzed for salinity concentration are preserved 

 in salinity sample bottles. The type of bottle 

 used by the Hydrographic Office has a glass 

 or porcelain stopper with a rubber gasket 

 which is attached to the bottle neck with a wire 

 clamp-on device. The bottles are numbered 

 on top of the stopper or on the side of the 

 bottle. They are shipped and stored in 

 compartmented wooden cases. 



Before drawing the sample, the salinity 

 bottle must be thoroughly rinsed twice with 

 water from the Nansen bottle. To do this, 

 fill the bottle about one-fourth full and shake 

 vigorously. Empty the rinse water in such 

 a manner that it washes the stopper and gasket. 

 Be sure to do this at least twice. 



Draw the water sample directly from the 

 drain petcock and fill the bottle to within one 

 inch of the top. A 1-inch air space must be 

 left to prevent the bottle from breaking due 

 to warming or freezing of the sample. The 

 stopper is then placed in the mouth and the 

 clamp-on device pulled securely down. 



After all salinity samples are drawn and 

 logged, they are placed in their shipping case. 

 If they are to be analyzed aboard ship they 

 must be placed in the laboratory for a minimum 

 of 6 hours before analysis. Eight to 12 hours 

 is preferable in order to allow them to come to 

 the same temperature as the room, apparatus, 

 and chemical solutions to be used in the 

 analyses. 



2 29 Drawing Sea Water Samples for 

 Nutrient Analyses. — Sea water samples for 

 various nutrient analyses are drawn in the same 

 manner as given for salinity samples. 



2-30 Draining the Nansen Bottle. — After 

 all the required sea water samples have been 

 drawn from the Nansen bottle, the remaining 

 water must be drained before the thermometers 

 are read. While the bottle remains in the rack, 

 the air vent and petcock should be left open. 

 However, be sure to close the air vent and drain 



petcock before lowering the bottle on a sub- 

 sequent cast. 



2-31 Storing and Shipping Sea Water 

 Samples. — Sea water samples to be analyzed 

 at the Hydrographic Office must be shipped in 

 wooden cases supplied for that purpose. On 

 the inside of the lid of each box is a label to 

 identify the samples upon arrival. Complete 

 this form giving all required cruise, station, 

 and sample bottle numbers. The shipping 

 case must be sealed in such a way that there 

 will be no danger of its opening in transit. 

 Give the ship's name and cruise number on the 

 outside of the case and address the case as 

 follows : 



The Hydrographer 



U. S. Navy Hydrographic Office 



Washington 25, D. C. 



(Code 5430) 



2-32 INSTRUCTIONS FOR OPERATING 

 THE BATHYTHERMOGRAPH.— The bathy- 

 thermograph, or BT, is an instrument for ob- 

 taining a permanent, graphical record of water 

 temperature (° F.) against depth (feet) as it is 

 lowered and raised in the ocean (fig. 2-8 and 

 2-9). A depth element in the instrument drives 

 a smoked-glass slide at right angles to a stylus 

 which in turn is driven by a thermal element. 

 The BT is lowered into the sea and retrieved by 

 means of a wire rope, boom, and winch. A 

 smoked-glass slide is inserted before lowering 

 and removed after each submersion. The trace, 

 or record scribed by the stylus, is read by 

 comparing with a grid individually calibrated 

 for each instrument, using a magnifying grid 

 viewer. The slide is preserved by dipping in 

 lacquer, properly draining, drying, and storing. 



2-33 The BT AssembIy.~The BT consists 

 essentially of a thermal element; a pressure, 

 or depth, element; a body tube; a nosepiece; 

 a nose sleeve; tailfins; and body tube sleeve. 



2-34 How a BT Works.— The bathythermo- 

 graph is designed to obtain a record of the 

 temperature of sea water at moderate depths. 

 It can be operated while the ship is underway 

 at speeds up to 18 knots. It works most satis- 

 factorily, however, at speeds of 12 knots or less. 



The thermal element, corresponding to the 

 mercury column in a glass thermometer, con- 

 sists of about 45 to 50 feet of fine copper tubing 

 filled with .xylene. The tubing is wound around 

 inside the tailfins of the BT and comes into 

 direct contact with the sea water. As the 

 xylene expands or contracts with the changing 

 water temperature, the pressure inside the 

 tubing increases or decreases. This pressure 

 change is transmitted to a Bourdon tube, a 



16 



H. O. 607 



