line. The signals, interpolated electronically, are used to record 

 only the depth of whole-degree-centigrade isotherms on 19-inch- 

 wide tape, which equals, in data acquisition, that derived from the 

 lowering of a bathythermograph every 120 feet at a ship's speed of 

 6 knots. The surface temperature, recorded by the uppermost 

 thermistor bead, and the depth of the deep extremity of the chain, 

 recorded by a pressure sensor, are printed on the same tape. The 

 oceanographic research vessel, towing the thermistor chain sus- 

 pended nearly vertical from the fantail, cruises forward and ac- 

 quires sea temperature structure data to a depth of 800 feet. Two- 

 dimensional coverage, depth and distance, is thus achieved (fig. 2); 

 however, time, a third dimension, must also be considered. The 

 small change in depth at the end of the chain, caused by the forward 

 movement of the ship, is disregarded in the following analysis. 



i 



Figure 2. Thermistor-chain towing technique used to acquire a two-dimensional 

 measurement of sea temperature structure. 



