INTRODUCTION 



The NEL thermistor chain has been in operation since 1961 

 and is capable of measuring and recording vertical sections of sea 

 temperature structure from the surface down to a depth of 800 

 feet. USS MARYSVILLE (EPCE(R) 857), from which the chain is 

 operated (fig. 1), conducted Cruise 1, the first test of this equip- 

 ment, over the nearby San Diego Trough in June 1961, and the re- 

 sults have been reported. ■'^ Cruise 2 was made between 10 and 14 

 July 1961 off Southern California.^ Cruise 3 entailed a test near 

 San Clemente Island. 



Cruise 4, the subject of this report, was from San Diego, 

 California, to Honolulu, Hawaii (fig. 2). The purpose was to 

 study the nature of vertical variations in temperature structure of 

 internal waves in the deep ocean regions well away from shore. 



Figure 1. NEL thermistor cho/n hoist used on USS MARYSVILLE to obtain data. 



