Page 405 



EQUIPMENT AND INSTRUMENTS 



4721 



4721. Tanner-Sigsbee Reversing Frame , 



The Tanner-Sigsbee reversing frame {B in figs. 86 and 87) is designed for only one 

 thermometer, which is held in a slotted metal tube holder by means of two helical springs 

 one at each end of the tube. The springs press against rubber cushions in which the 

 ends of the thermometer rest. The lower end of the holder is hinged to the bottom of 

 the frame, the upper end being held in place by a pin. The pin is the lower end of a 

 coarse-threaded shaft to the top of which a propeller is attached. The blades of the 

 propeller are arranged so that downward passage through the water forces the pin into 

 the small hole in the top of the holder, maintaining it upright, but as soon as the frame 



B C 



Figure 87. — Same oceanographic instruments after sounding. 



on 



is drawn upward, the propeller revolves withdrawing the pin from the hole so that 

 the holder is free to capsize. The pitch of the propeller is large enough so that raising 

 it through less than 6 feet of water will withdraw the pin. The frame is clamped at top 

 and bottom to the sounding line by a long spring. 



To assemble the reversing fi-ame for use, the top of the holder is unscrewed and the upper spring 

 and rubber cushion are removed from the thermometer holder; the reversing thermometer is inserted 

 in the holder vi^ith the large mercury reservoir towards the hinged end and turned so that the gradu- 

 ated scale will be visible through the long slot in the holder. The top spring is replaced with the 

 rubber cushion against the thermometer and compressed while the top is screwed to the holder. The 

 holder is secured in an upright position by revolving the propeller until the pin engages the hole. The 

 frame is now ready to be clamped to the sounding line. The propeller end of the frame must be upper- 

 most when it is lowered into the water. Since the clamp is likely to slip on sounding wire, a short 

 section of leadline material, to which the frame may be clamped, must be inserted between the wire 

 and the sounding lead. The reversing frame must be attached to the sounding line high enough above 

 other instruments so that the thermometer holder will not strike them when it is inverted. 



