Figure C-7. Inserting glass slide into BT. 



Figure C-8. BT just below the surface. 



point in the operation. To bring the BT along- 

 side and raise it without too much swing re- 

 quires practice. 



Stop the winch with tlie BT 2 or 3 feet from 

 the towing block. If the BT skips or swings 

 forward of the boom, allow the BT to sink 

 freely until it has passed clear astern, and try 

 again. 



Turn off the winch motor and commence 

 bringing the BT aboard. The BT can be brought 

 aboard m various ways, depending on how the 

 boom is rigged. With the standard gate boom, 

 the use of a retrieving line and ring is recom- 

 mended (fig. C-10). This consists of a metal 

 ring an inch and a half in diameter through 

 which the wire is passed between the towing 

 block and the BT. The ring is attached to a 

 retrieving line which is secured to the lifeline 



Reading the sea surface reference 

 temperature. 



or rail. With the proper amount of slack, the 

 ring will ride freely when the BT is being 

 lowered and retrieved. By hauling in on the 

 retrieving line while easing the brake, the BT 

 can be brought to hand. 



Step 8. Kemoving the BT Slide. — As soon 

 as the BT is in hand, slack off the wire, set the 

 brake, and remove the BT slide in the follow- 

 ing manner : 



Move the sleeve forward toward the BT nose 

 to lift the stylus off the slide. Partially eject the 

 slide by pushing against its edge with the fore- 

 finger, or a pencil, through the slide-ejecting 

 part (fig. C-11). 



Carefully, grip the slide by the thumb and 

 forefinger (fig. C-12) holding the slide only by 

 the edges. Be careful not to obscure the trace 

 with smudges or fingerjirints. 



Place the BT in its deck rack, and notify the 

 bridge that the BT is on deck. 



Step 9. Securing Equipment. — If another 

 lowering is to be made soon and there is no dan- 

 ger of overheating the BT, it may be left in the 

 deck rack connected to the wire ; otherwise, un- 

 shackle it and stow in a cool plac«. CAUTION ; 

 Never let the temperature of the BT exceed 

 105° F. (40..56° C). If this temperature is ex- 

 ceeded, the instrument will be damaged and the 

 calibration will be invalid. Never leave the BT 

 on deck without protection from hot sun. Suit- 

 able protection to the thermal element can be 

 afforded by keeping the BT covered with wet 

 cloths. 



Step 10. Labeling the BT Slide.— As soon as 

 the BT slide is removed from the BT, examine 



C-5 



