Figure 2-11. Lowering the bathythermograph. 



corded by the BT, and plot a graph showing 

 counter reading against depth for various ship's 

 speeds. 



When the counter indicates that the proper 

 length of wire has been payed out, or when the 

 last layer of wire on the drum has been reached, 

 the brake should be applied smoothly allowing 

 the drum to stop without a sudden jerk. An 

 excessive jerk will part the wire. The BT will 

 now swim back up to near the surface far 

 astern. Check to see that the wire leads 

 properly for hauling in. If it does not lead from 

 the towing block to the center of the drum ad- 

 just the boom guys until it does. 



2-46 Haul in'lhe BT.— Move the hand lever 

 smartly from the brake position to the hoist 

 position. Do not pause while going through 

 neutral or more wire will pay out. Guide the 

 wire back and forth in even layers on the drum 

 using the 15-inch stick. The end of an old 

 swab handle will do. Do not use a metal guide. 

 If kelp or gulfweed fouls the wire, ease on the 



H. O. 607 



350676 0—56 'A 



brake and clear the wire with a boathook. 

 Haul in at full speed until it is seen from the 

 counter and by rapid decrease in the wire angle 

 that the BT is close astern but still a safe dis- 

 tance from the ship's screws. 



2-47 Bring the BT Aboard.— When only 

 about 100 feet of wire is out, the BT should be 

 readily visible at the surface. As the wire is 

 hauled in, the BT will reach a position nearly 

 under the boom where it will begin to porpoise, 

 breaking clear of the surface and swinging 

 forward as the ship rolls or as wave crests pass. 

 This is the most critical point in the operation. 

 To bring the BT alongside and raise it without 

 too much swing requires practice. If the BT is 

 brought in too fast, it may skip or swing forward 

 of the boom, perhaps hitting the side of the ship 

 or swinging completely over the boom. If the 

 BT skips or swings forward of the boom, it is 

 advisable to shift at once to neutral and allow 

 the BT to sink freely until it has passed clear 



21 



