A bucket can be made by obtaining a half- 

 gallon can 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 

 thermometer into the bucket so that at least 

 3 inches of the bulb end is immersed in sea 

 water. Stir the thermometer with a circular 

 motion for 15 to 20 seconds and then read it 

 vnth the stem still immersed in the water. Stir 

 it once or twice more and check the reading 

 (fig. 2-10). 



Figure 2-10. Taking the bucket temperature. 



It is important that the bucket sample be 

 taken at the time the BT is being towed and 

 that the temperature reading be made as soon 

 as possible after the sample is on deck. If the 

 sample is allowed to stand for more than 45 

 seconds the temperature reading will be no 

 longer valid. It is also important to stir the 

 thermometer to bring it to temperature more 

 rapidly and accurately. 



2-44 Lower the BT. — Move the winch lever 

 to the neutral position and allow the wire to 



20 



pay out freely. Success in reaching the maxi- 

 mum desired depth depends primarily on two 

 factors; (1) having the winch drum and towing 

 block bearings well lubricated to minimize 

 friction and (2) getting the BT down below the 

 ship's screw wash as soon as possible. With 

 practice, it is possible to raise the BT slightly 

 after the 30 seconds of towing at the surface is 

 completed. Skip it off the crest of a wave so 

 that it swings forward, and then lower rapidly. 

 This enables the BT to plunge into the water and 

 its momentum will carry it more rapidly past the 

 turbulence of the wash and will enable it to 

 reach a greater depth. This technique is 

 especially useful with the 900-foot instrument. 

 It takes practice, but to the experienced oper- 

 ator is easier to use and more effective than the 

 diving lug assembly attached to some models 

 (fig. 2-11). 



When the ship is making more than 12 knots, 

 there usually is enough drag on the wire while 

 the BT is diving to insure that it will not slacken 

 and backlash. At lower speeds, and during 

 heavy rolling, the wire may slack between the 

 winch and the towing block. This may cause 

 backlash on the winch drum or a kink at the 

 towing block. The operator should provide 

 himself with a round stick about 15 inches long 

 to be used to gently slow the drum when exces- 

 sive slack appears. Do not apply too much 

 pressure to the drum with the stick because once 

 the diving motion of the BT is arrested it will 

 not dive further regardless of the amount of 

 wire payed out. Do not touch the wire with 

 your hands when the drum is in motion; you 

 may be seriously injured. 



2-45 Stop at the Proper Depth. — To reach a 

 given depth, the amount of cable to be payed 

 out will depend upon the speed of the ship, the 

 type of BT, and whether or not the nose sleeve 

 is attached. The table below provides a rough 

 estimate of speeds at which full depth may be 

 expected to be reached when using 1,000 feet of 

 wire. 



The observer should take data on the length 

 of wire payed out and the actual depths re- 



H. O. 607 



