Chapter 5 — BATHYTHERM03RAPH 



and the clutch is toward the operator. Check 

 these operating positions to make sure that 

 the installation is correct and that the drum 

 revolves freely in neutral. 



Step 4— Put Slide in BT 



Remove the waterproof cover from the box 

 of glass slides and take out one slide at a time, 

 holding the slide by the edges to avoid damaging 

 the metallic film. Do not remove the waterproof 

 cover from the box until actually ready to use 

 the slides. 



Insert the slide into the hole on the side of 

 the BT as shown in figure 5-7 and push it into 

 its bracket. The edge of the slide with the 

 beveled corners goes in first, the longer bevel 

 toward the nose of the BT. Make certain that 

 the plated surface of the slide is toward the 

 stylus. Push the slide in all the way against 



Figure 5-7. 



71.77 

 -Inserting the slide. 



the stop pin. The slide must be fully in, other- 

 wise the temperature recorded will be fictitiously 

 low. Check the grooves of the slide holder to 

 ensure that they are clean, free of glass chips, 

 and that the spring holds the slide firmly against 

 the opposite groove. With the slide fully in, the 

 stylus is brought against the plated surface when 

 the sleeve is moved back to cover the opening. 

 To reduce extraneous scratches on the slide, 

 do not move the sleeve back until the BT is 

 ready to be put over the side. 



Step 5 — Put BT Over the Side 



After obtaining permission from the OOD to 

 make a lowering, pick up the BT and pull the 

 sleeve down over the slide port. On the shallow 

 and medium depth models, pull the sleeve down 

 toward the tail as far as possible so as to engage 

 the catch of the stylus lifter, then push the sleeve 

 up toward the nose about 1 inch. This action 

 leaves the port open enough for the catch to 

 release when the BT is retrieved. On the 900- 

 foot model, the sleeve should remain all the way 

 back toward the tail. Set the winch lever in 

 neutr;il. With one hand, hold the BT at the rail; 

 with the other, take up the slack in the wire by 

 rotating the drum. Set the brake when all slack 

 is in. 



When ready to commence lowering, set the 

 winch lever to neutral and lower the BT into 

 water to such a depth that it tows smoothly just 

 below the surface. Put on the brake and hold the 

 BT there for 1 minute to enable the thermal 

 element to come to the temperature of the 

 surface water. Set the winch counter at zero. 



Step 6 — Take Bucket Temperature 



While the BT is being towed at the surface, 

 take the bucket temperature of the surface 

 water and record it on the bathythermograph 

 log sheet. Special bucket thermometers are 

 supplied for U.S. Navy surveys by the Oceano- 

 graphic Office. These special bucket thermo- 

 meters arc more accurate than thermometers 

 issued with the BT kits, and are to be used in 

 lieu of the ones in the kits. The thermometers 

 are read to the nearest 0.1°F. 



A bucket can be made from a half-gallon can 

 (obtained from the galley) and attaching a line 

 to it. Attach the bitter end of the line to the 

 lifeline or rail. Throw the can over the side 

 and let it fill and empty several times before 

 hauling a surface sample aboard. As soon as 

 it is aboard, set it on deck and insert the 



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