68 Hydrogen-ion Concentration and Electrical Conductivity 



dependent upon the season. This fact has been known since the 

 voyage of the Challenger in 1873 (Narrative of the Challenger Expedi- 

 tion, vol. 1, part 2, p. 758, chart No. 19). I have crossed the equator 

 in about longitude 165° W. eight times since 1917, and at or near the 

 equator we usually entered a region wherein the surface water was of 

 lower temperature than to the northward or southward of this place 

 (table 3). 



Table 3. 



* At 5 p. m. September 20 current was strong easterly until 9 p. m. 



It will be seen that on six of these eight voyages we crossed a region 

 of low temperature near the equator, with warmer water both to the 

 north and to the south of it. Moreover, on five of the eight voyages 

 we encountered a surface current setting toward the east in this region, 

 and thus contrary to the prevailing westerly drift of the surface water 

 over the tropical belt of the Pacific. Now, it is well known that a 

 surface current moving toward the west will set up a current toward 

 the east in the deeper waters. This subject has been admirably 

 treated by W. J. Sandstrom in his Hydrodynamics of Canadian 



