astern and is safe to try again. The operator 

 must learn the feel of his own winch. 



With a little patience the BT can be brought 

 safely to within 2 or 3 feet of the towing block. 

 The winch motor should be turned off at this 

 point, eliminating the possibility of accidentally 

 jamming the BT against the towing block. 



The BT can then be brought aboard in 

 various ways, depending on how the boom is 

 rigged. With the standard gate boom, the 

 use of a retrieving line and ring is recommended. 

 This consists of a metal ring of an inch to an 

 inch and a half in diameter through which the 

 wire is passed between the towing block and 

 the BT. To the ring is attached a retrieving 

 line which is secured to the lifeline or rail. 

 With the proper amount of slack, the ring 

 will ride freely when the BT is being lowered 

 and hoisted. By hauling in on the retrieving 

 line while easing the brake the BT can be 

 easily brought to hand (fig. 2-12). If a re- 

 trieving line is not used, then it will be necessary 

 to rig in the boom by casting off the after guy 

 and swinging the boom in with the forward guy. 

 Two men can pull it in with a boathook — one 

 man on the hook and the other to slack the wire 

 with the winch. If the boom tops up, the 



Figure 2-12. Bringing in the BT with a retrieving line. 



BT can be brought aboard by one man hauling 

 in on the topping lift. 



2-48 Remove the Slide and Secure the 

 Equipment. — As soon as the BT is in hand move 

 the sleeve forward toward the nose to lift the 

 stylus off the slide. This prevents the upper 

 portion of the trace from being affected by air 

 temperature and becoming obscured as the 

 instrument is handled. 



Slack off the wire, place the BT in its deck 

 rack, and set the brake. Notify the bridge 

 that the BT is on deck. Partially eject the 

 slide by pushing against its edge with the 

 forefinger, the wire slide remover, or a pencil 

 through the slide-ejecting port. Grip the slide 

 carefully by the thumb and forefinger. Hold 

 the slide only by the edges, being careful not 

 to obscure the trace with smudges or finger- 

 prints. 



If another lowering is to be made soon and 

 there is no danger of overheating the BT, it 

 may be left in the deck rack connected to the 

 wire; otherwise unshackle it and stow in a cool 

 place. 



CAUTION 



Never let the temperature of the BT 

 exceed 105°F. (40.8°C). If the tem- 

 perature is exceeded, the calibration 

 of the instrument will be damaged. 

 Never leave the BT on deck without 

 protection from hot sun. Suitable 

 protection to the thermal element can 

 be afforded by keeping it covered with 

 wet cloths. 



2-49 Label the BT Slide.— As soon as the 

 slide is removed from the BT, examine it to 

 be sure that a suitable trace has been obtained. 

 Sometimes the smoked surface washes away 

 on contact with sea water. If this has occurred, 

 lower the BT again with a fresh slide. If 

 it recurs, follow instructions given in section 

 2-58. With a sharp pencil, write the following 

 information on the slide, being careful not to 

 obscure or touch the temperature-depth trace 

 (fig. 2-13). 



(1) Cruise and slide serial number. — Give the 

 ship and cruise number followed by the con- 

 secutive serial number of each slide. Thus 

 the first slide taken on the fifteenth cruise of 

 USS Rehoboth would be RE-15-]. The last 

 figure is the serial number recorded in the first 

 column of the B-sheet. 



(2) Time group. — The second line contains 

 the 4-digit time group. Use Greenwich mean 

 time (0001 to 2400), giving the hour and minute 

 at which the BT enters the water. 



22 



H. O. 607 



